Table Of ContentGo for DevOps
Learn how to use the Go language to automate
servers, the cloud, Kubernetes, GitHub, Packer,
and Terraform
John Doak
David Justice
BIRMINGHAM—MUMBAI
Go for DevOps
Copyright © 2022 Packt Publishing
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Monika, you are the North Star I guide my ship with and I love you with all
my heart. I couldn't have done this without your support and guidance.
– John Doak
To Deya, Will, Thor, and Tron, without whom my days would be as muted
and monotone as this page.
– David Justice
Contributors
About the authors
John Doak is the principal manager of Layer 1 Reliability Engineering at Microsoft. John
led the development of the Azure Data Explorer and Microsoft Authentication Library
Go SDKs. Previously, he was a Staff Site Reliability Engineer at Google. As part of network
engineering, he created many of their first network automation systems. John led the
migration of that group from Python to Go, developing Go training classes that have been
taught around the world. He was a pivotal figure in transforming the network team to a
network/systems group that integrated with SRE. Prior to that, he worked for Lucasfilm in
video games and film. You can find his musings on Go/SRE topics and his Go classes on
the web.
I'd like to thank Raleigh Mann who was my manager at both Lucasfilm and
Google during most of my time there. His advice and steadfastness when
standing beside me are why I still call him Boss today. Stephen Stuart, who
gave me my initial foray into management, which I'm not sure I should
thank or curse him for. Thanks to Less Lincoln, the man, the myth, the
legend. I’ve worked with Less for four years, he’s as much a mystery box as
when I first met him (and I think he likes it that way). Of course, I would
never have gotten here without the love and support of my parents, I love
you both. Thanks to Sarah Murphy, who was an early contributor to the
book. And thanks to David Justice. Without his hard work and enthusiasm,
I would not have been able to do this.
David Justice is the principal software engineer lead for the Azure K8s infrastructure
and Steel Thread teams, which maintain a variety of CNCF and Bytecode Alliance
projects. He is a maintainer of the Cluster API Provider Azure and a contributor to the
Cluster API. Prior to that, David was the technical assistant to the Azure CTO, where
he was responsible for Azure cross-group technical strategy and architecture. Early
on at Microsoft, he was a program manager leading Azure SDKs and CLIs, where he
transitioned all Azure services to describe them using OpenAPI specifications in GitHub
and established automations to generate Azure reference docs, SDKs, and CLIs. Prior to
working at Microsoft, David was the CTO of a mobile CI/CD SaaS called CISimple.
Thank you to my lovely, supportive wife, Deya, for encouraging me to
pursue time-consuming activities such as writing a book, educational
pursuits, start-ups, and her favorite, golf. Deya and Will, you will never
know how much your love, hugs, and support powered me through late
nights and droughts of creativity. This book would not be possible without
the brilliance, reliability, and counter-perspectives of my coauthor, John, for
whom the word example means a 30k-line robust application. Thank you
to the whole Packt team and all the reviewers, but especially Romy Dias
who edited my work into something more closely resembling English prose.
Finally, thank you Dad and Papa for always believing in me.
About the reviewers
Trieu Pham is a software engineer with various technical ideas. His current focus
and specialty are on API development, microservices, DevOps, and Golang. He has a
bachelor's degree in mathematics and computer science, a master's degree in computer
engineering, and a PhD in engineering.
Lukasz Sudol is a senior director of engineering at GumGum. He began working in the
e-commerce industry by developing backend systems. During the past decade, his work
has focused on developing high-availability application architectures for AdTech. He
enjoys helping people to develop and working with interesting technologies.
I would like to thank my family, my fiancée Marcelina, and my friends
who understand the time and commitment it takes to research and test
engineering tools that are constantly changing. And to the reader, I hope my
contribution will help you get through the book more easily.
Table of Contents
Preface
Section 1: Getting Up and Running with Go
1
Go Language Basics
Technical requirements 5 Using conditionals 24
Using the Go Playground 5 if statements 24
Utilizing Go packages 7 else 25
Declaring a package 7 Learning about functions 28
Importing a package 8
Returning multiple values
Using a package 9
and named results 29
Package name conflicts 9
Variadic arguments 30
Packages must be used 10
Anonymous functions 31
A Go Hello World 11
Defining public and
Using Go's variable types 12 private 32
Go's types 14 Using arrays and slices 34
Declaring variables 15
Arrays 34
Variable scopes and shadowing 17
Slices 35
Function/statement variable
Extracting all values 36
must be used 20
Understanding maps 37
Looping in Go 21 Declaring a map 37
C style 21 Accessing values 38
Removing the init statement 21 Adding new values 38
Remove the post statement Extracting all values 39
too and you have a while loop 22
Understanding Go
Creating an infinite loop 22
pointers 39
viii Table of Contents
Memory addresses 40 Changing a field's value in
Function arguments are a method 47
copies 40 Constructors 48
Pointers to the rescue 41
Comprehending Go
Getting to know about interfaces 49
structs 43 Defining an interface type 49
Declaring a struct 43 Important things about
Declaring a custom type 44 interfaces 50
Custom struct types 44 The blank interface – Go's
Adding methods to a type 45 universal value 51
Changing a field's value 46 Type assertion 51
Summary 52
2
Go Language Essentials
Handling errors in Go 54 Channels 69
Creating an error 54 Sending/receiving 70
Using an error 55 select statements 71
Creating named errors 56 Channels as an event signal 72
Custom errors 57 Mutexes 74
Wrapping errors 58 RWMutex 75
Utilizing Go constants 59 Understanding Go's
Context type 75
Declaring a constant 59
Enumeration via constants 61 Using a Context to signal
a timeout 76
Printing enumerators 62
Honoring a context when
Using defer, panic, and receiving 77
recover 63 Context in the standard
defer 63 library 78
panic 64 Context to pass values 79
recover 64 Best practices 81
Utilizing goroutines Utilizing Go's testing
for concurrency 65 framework 81
Starting a goroutine 66 Creating a basic test file 82
Synchronization 67 Creating a simple test 83
WaitGroups 68 Table Driven Tests (TDT) 84
Table of Contents ix
Creating fakes with interfaces 86 Type constraints with
Third-party testing packages 90 methods 95
Adding type parameters to struct
Generics – the new kid
types 96
on the block 91
Specifying the type when
Type parameters 91 calling a generic function 98
Using type constraints 92 Gotchas to watch for 100
We could do better with When to use generics 101
constraints 93
Summary 102
Current built-in constraints 94
3
Setting Up Your Environment
Technical requirements 103 A note on Go compiler
version compatibility 108
Installing Go on your
machine 104
Building code locally 108
macOS installation using the
Creating a module directory
package installer 104
and go.mod file 109
macOS installation via
Updating a module when
Homebrew 104
adding dependencies 110
Windows installation using
Adding a hello world 110
MSI 105
Running our first program 110
Linux 106
Other platforms 108 Summary 111
4
Filesystem Interactions
All I/O in Go are files 114 Stdin/Stdout/Stderr are just
files 119
I/O interfaces 114
Reading data out of a
Reading and writing to stream 120
files 115 Writing data into a stream 122
Reading local files 115
OS-agnostic pathing 123
Writing local files 116
What OS/platform am
Reading remote files 117
I running? 124
Streaming file content 119 Using filepath 124
