One of the peculiarities of a Go map is that the fields return in a random order.
If you run this simple example:
package main
import (
"fmt"
)
func main() {
ages := map[string]int{
"a": 1,
"c": 3,
"d": 4,
"b": 2,
}
fmt.Println(ages)
fmt.Println(ages)
fmt.Println(ages)
}
the output will be
map[b:2 a:1 c:3 d:4]
map[c:3 d:4 b:2 a:1]
map[d:4 b:2 a:1 c:3]
This is on purpose, to avoid relying on the items order, as different implementations of the compiler might use different hash functions. It’s one of those things that make Go very explicit in avoiding causing invalid assumptions.
What if you want to order a map by key?
package main
import (
"fmt"
"sort"
)
func main() {
ages := map[string]int{
"a": 1,
"c": 3,
"d": 4,
"b": 2,
}
names := make([]string, 0, len(ages))
for name := range ages {
names = append(names, name)
}
sort.Strings(names) //sort keys alphabetically
for _, name := range names {
fmt.Println(ages[name])
}
}
This program will print the values of the map, ordered by key:
1
2
3
4
More go tutorials:
- Using NGINX Reverse Proxy to serve Go services
- Making a copy of a struct in Go
- The basics of a Go Web Server
- Sorting a map type in Go
- Go pointers in a nutshell
- Go Tags explained
- Go Date and Time Formatting
- JSON processing with Go
- Go Variadic Functions
- Go Strings Cheat Sheet
- The Go Empty Interface Explained
- Debugging Go with VS Code and Delve
- Named Go returns parameters
- Generating random numbers and strings in Go
- Filesystem Structure of a Go project
- Binary Search Algorithm Implemented in Go
- Using Command Line Flags in Go
- GOPATH Explained
- Build a Command Line app with Go: lolcat
- Building a CLI command with Go: cowsay
- Using Shell Pipes with Go
- Go CLI tutorial: fortune clone
- List the files in a folder with Go
- Use Go to get a list of repositories from GitHub
- Go, append a slice of strings to a file
- Go, convert a string to a bytes slice
- Visualize your local Git contributions with Go
- Getting started with Go CPU and memory profiling
- Solving the "does not support indexing" error in a Go program
- Measuring execution time in a Go program
- Building a Web Crawler with Go to detect duplicate titles
- Go Best Practices: Pointer or value receivers?
- Go Best Practices: Should you use a method or a function?
- Go Data Structures: Set
- Go Maps Cheat Sheet
- Generate implementations for generic types in Go
- Go Data Structures: Dictionary
- Go Data Structures: Hash Table
- Implement Events Listeners in Go through Channels
- Go Data Structures: Stack
- Go Data Structures: Queue
- Go Data Structures: Binary Search Tree
- Go Data Structures: Graph
- Go Data Structures: Linked List
- The complete guide to Go Data Structures
- Comparing Go Values
- Is Go object oriented?
- Working with a SQL Database in Go
- Using environment variables in Go
- Go tutorial: REST API backed by PostgreSQL
- Enabling CORS on a Go Web Server
- Deploying a Go Application in a Docker Container
- Why Go is a powerful language to learn as a PHP developer
- Go, remove the io.Reader.ReadString newline char
- Go, how to watch changes and rebuild your program
- Go, count the months since a date
- Accessing HTTP POST parameters in Go