Mastering Go: Leverage Go's expertise for advanced utilities, empowering you to develop professional software. 4 Ed

Cover....1 Copyright....3 Contributors....4 Table of Contents....8 Preface....24 Chapter 1: A Quick Introduction to Go....32 Introducing Go....33 The history of Go....33 The advantages of Go....35 When to use Go....36 My personal Go journey....37 The go doc and godoc utilities....38 Hello World!....39 Introducing functions....40 Introducing packages....41 Running Go code....41 Compiling Go code....41 Using Go like a scripting language....42 Important formatting and coding rules....42 What you should know about Go....44 Defining and using variables....44 Constants....45 Global variables....45 Printing variables....45 Controlling program flow....47 Iterating with for loops and range....50 Getting user input....52 Reading from standard input....53 Working with command line arguments....53 Using error variables to differentiate between input types....57 Understanding the Go concurrency model....60 Developing the which(1) utility in Go....62 Logging information....64 log.Fatal() and log.Panic()....66 Writing to a custom log file....68 Printing line numbers in log entries....70 Writing to multiple log files....71 Developing a statistics application....72 Summary....75 Exercises....75 Additional resources....75 Chapter 2: Basic Go Data Types....78 The error data type....79 Numeric data types....83 Avoiding overflows....85 Non-numeric data types....86 Strings, characters, and runes....87 Converting int to string....89 The unicode package....90 The strings package....91 Times and dates....94 Working with different time zones....96 Constants....97 The constant generator iota....97 Typed and untyped constants....100 Grouping similar data....101 Arrays....101 Slices....101 About slice length and capacity....104 Selecting a part of a slice....107 Byte slices....109 Deleting an element from a slice....111 How slices are connected to arrays....114 Catching out of bounds errors....116 The copy() function....117 Sorting slices....119 Pointers....121 Converting a slice to an array or an array pointer....125 Data types and the unsafe package....126 Generating random numbers....128 Generating random strings....130 Generating secure random numbers....131 Updating the statistics application....132 Summary....133 Exercises....134 Additional resources....134 Chapter 3: Composite Data Types....136 Maps....137 How to tell whether a key exists on a map....138 Storing to a nil map....138 Iterating over maps....140 Structures....141 The type keyword....141 Defining new structures....141 Using the new keyword....143 Slices of structures....145 Regular expressions and pattern matching....147 About regexp.Compile and regexp.MustCompile....147 Go regular expressions....149 About raw string and interpreted string literals....150 Matching names and surnames....150 Matching integers....151 Improving the statistics application....152 Working with CSV files....152 The updated version of the statistics application....157 Summary....160 Exercises....161 Additional resources....161 Chapter 4: Go Generics....164 An introduction to generics....165 Hello, generics!....166 Constraints....167 Creating constraints....168 Supporting underlying data types....170 Supporting slices of any type....171 Defining new data types with generics....171 Using generics in Go structures....173 The cmp package....176 The slices package....176 Shallow and deep copies....177 The maps package....179 When to use generics....181 Summary....182 Exercises....182 Additional resources....183 Chapter 5: Reflection and Interfaces....184 Reflection....185 Understanding the internal structure of a Go structure....186 Changing structure values using reflection....189 The three disadvantages of reflection....190 Type methods....191 Creating type methods....191 Value and point receivers....192 Using type methods....193 Interfaces....196 The sort.Interface interface....199 The empty interface....201 Type assertions and type switches....203 The map[string]interface{} map....208 The error data type....212 Writing your own interfaces....215 Using a Go interface....216 Object-oriented programming in Go....217 Interfaces versus generics....221 Reflection versus generics....224 Updating the statistics application....226 Summary....229 Exercises....230 Additional resources....230 Chapter 6: Go Packages and Functions....232 Go packages....233 About go get and go install....234 Functions....237 Anonymous functions....237 Functions that return multiple values....238 The return values of a function can be named....239 Functions that accept other functions as parameters....240 Functions can return other functions....242 Variadic functions....243 The defer keyword....247 Big O complexity....250 Developing your own packages....250 The init() function....251 Order of execution....252 Using GitHub to store Go packages....254 A package for working with SQLite....255 Working with SQLite3 and Go....256 Storing the Go package....265 The design of the Go package....265 The implementation of the Go package....266 Testing the Go package....275 Modules....281 Creating better packages....281 Generating documentation....283 Workspaces....288 Versioning utilities....291 Summary....293 Exercises....294 Additional resources....294 Chapter 7: Telling a UNIX System What to Do....296 stdin, stdout, and stderr....297 UNIX processes....297 File I/O....298 The io.Reader and io.Writer interfaces....298 Using and misusing io.Reader and io.Writer....299 Buffered and unbuffered file I/O....303 Reading text files....304 Reading a text file line by line....304 Reading a text file word by word....306 Reading a text file character by character....307 Reading from /dev/random....309 Reading a specific amount of data from a file....310 Writing to a file....311 Working with JSON....314 Using Marshal() and Unmarshal()....314 Structures and JSON....316 Reading and writing JSON data as streams....318 Pretty printing JSON records....319 The viper package....321 Using command line flags....321 Reading JSON configuration files....324 The cobra package....328 A utility with three commands....330 Adding command line flags....330 Creating command aliases....331 Creating subcommands....332 Important Go features....333 Embedding files....333 ReadDir and DirEntry....336 The io/fs package....338 Updating the statistics application....340 The slog package....341 Sending logs to io.Discard....343 Using cobra....343 Storing and loading JSON data....345 Implementing the list command....346 Implementing the insert command....347 Summary....348 Exercises....349 Additional resources....349 Chapter 8: Go Concurrency....352 Processes, threads, and goroutines....353 The Go scheduler....354 The GOMAXPROCS environment variable....356 Concurrency and parallelism....357 Goroutines....358 Creating a goroutine....358 Creating multiple goroutines....359 Waiting for all goroutines to finish....360 What if the number of Add() and Done() calls differ?....362 Creating multiple files with goroutines....364 Channels....365 Writing to and reading from a channel....365 Receiving from a closed channel....368 Channels as function parameters....369 Race conditions are bad....370 The Go race detector....371 The select keyword....373 Timing out a goroutine....375 Timing out a goroutine inside main()....375 Timing out a goroutine outside main()....377 Go channels revisited....378 Buffered channels....379 nil channels....381 Worker pools....382 Signal channels....386 Specifying the order of execution for your goroutines....386 Handling UNIX signals....389 Handling two signals....392 Shared memory and shared variables....392 The sync.Mutex type....392 What happens if you forget to unlock a mutex?....394 The sync.RWMutex type....395 The atomic package....398 Sharing memory using goroutines....400 Closured variables and the go statement....403 The context package....405 About context.WithCancelCause....409 The semaphore package....410 Making the statistics application concurrent....413 Summary....416 Exercises....416 Additional resources....417 Chapter 9: Building Web Services....418 The net/http package....418 The http.Response type....419 The http.Request type....419 The http.Transport type....420 Creating a web server....421 Updating the statistics application....425 Defining the API....425 Implementing the handlers....426 Creating a Docker image....435 Developing web clients....437 Using http.NewRequest() to improve the client....439 Using errGroup....442 Creating a client for the statistics service....444 Timing out HTTP connections....450 Using SetDeadline()....450 Setting the timeout period on the client side....452 Setting the timeout period on the server side....454 Summary....455 Exercises....455 Additional resources....455 Chapter 10: Working with TCP/IP and WebSocket....458 TCP/IP....459 The nc(1) command line utility....460 The net package....460 Developing a TCP client....461 Developing a TCP client with net.Dial()....461 Developing a TCP client that uses net.DialTCP()....463 Developing a TCP server....465 Developing a TCP server with net.Listen()....465 Developing a TCP server that uses net.ListenTCP()....468 Developing a UDP client....470 Developing a UDP server....472 Developing concurrent TCP servers....475 Creating a WebSocket server....478 The implementation of the server....479 Using websocat....482 Creating a WebSocket client....484 Working with RabbitMQ....488 Running RabbitMQ....489 Writing to RabbitMQ....490 Reading from RabbitMQ....492 How to remove a module....494 Summary....494 Exercises....495 Additional resources....495 Chapter 11: Working with REST APIs....498 An introduction to REST....499 Developing RESTful servers and clients....501 A RESTful server....502 A RESTful client....511 Creating a functional RESTful server....521 The REST API....521 Using gorilla/mux....522 The use of subrouters....523 The Gin HTTP framework....524 Gin versus Gorilla....524 Working with the database....524 Implementing the RESTful server....529 Testing the RESTful server....534 Testing GET handlers....535 Testing POST handlers....536 Testing the PUT handler....537 Testing the DELETE handler....538 Creating a RESTful client....538 Creating the structure of the command line client....539 Implementing the RESTful client commands....540 Using the RESTful client....545 Working with multiple REST API versions....546 Summary....547 Exercises....547 Additional resources....548 Chapter 12: Code Testing and Profiling....550 Optimizing code....551 Rewriting the main() function for better testing....552 Profiling code....553 Profiling a command line application....554 Profiling an HTTP server....558 The web interface of the Go profiler....560 The go tool trace utility....562 Tracing a web server from a client....564 Visiting all routes of a web server....567 Testing Go code....571 Writing tests for ./ch03/intRE.go....572 Testing UNIX signals....574 Disabling test caching....577 The testing.TempDir() function....577 The Cleanup() function....577 The testing/quick package....580 Timing out tests....582 Testing using testing.T.Fatal() and testing.T.Fatalf()....583 Table-driven tests....585 Testing code coverage....587 Finding unreachable Go code....590 Testing an HTTP server with a database backend....593 The govulncheck tool....599 Installing the tool....599 Cross-compilation....603 Using go:generate....604 Creating example functions....607 Summary....608 Exercises....609 Additional resources....609 Chapter 13: Fuzz Testing and Observability....612 Fuzz testing....613 A simple fuzz testing example....614 An advanced fuzz testing example....617 Correcting the bug....623 Observability....629 The runtime/metrics package....630 Measuring the execution time of a function....632 The expvar package....634 Learning about CPU characteristics....636 Exposing metrics to Prometheus....638 Exposing metrics....638 Creating a Docker image for a Go server....642 Specifying the metrics to expose....644 Getting the metrics....647 Putting the metrics in Prometheus....648 Visualizing Prometheus metrics in Grafana....653 Summary....655 Exercises....655 Additional resources....655 Chapter 14: Efficiency and Performance....658 Benchmarking code....659 A simple benchmark scenario....660 Benchmarking the number of memory allocations....663 Initial version....663 Improving the number of memory allocations....664 Buffered versus unbuffered file I/O....668 The benchstat utility....672 Wrongly defined benchmark functions....674 Go memory management....675 Heap and stack....675 The main elements of the Go memory model....679 Memory leaks....679 Slices and memory leaks....680 Maps and memory leaks....682 Memory pre-allocation....683 Working with eBPF....685 What is eBPF?....685 About observability and eBPF....686 Creating an eBPF tool in Go....686 Summary....690 Exercises....690 Additional resources....690 Chapter 15: Changes in Recent Go Versions....692 About rand.Seed()....692 What is new in Go 1.21?....693 The sync.OnceFunc() function....693 The clear function....695 What is new in Go 1.22?....696 Changes in slices....697 Changes in for loops....698 The math/rand/v2 package....699 Summary....701 Exercises....701 Additional resources....701 Appendix: The Go Garbage Collector....704 Garbage collection....704 The key characteristics of the Go GC....705 Learning more about the Go GC....705 The tri-color algorithm....708 More about the operation of the Go GC....711 Maps, slices, and the Go GC....712 Using slices....712 Using maps with pointers....713 Using maps without pointers....714 Splitting a map....714 Comparing the performance of the presented techniques....715 Additional resources....716 Packt Page....718 Other Books You May Enjoy....720 Index....724