Quick Golang 0
| Concept | Go | JS | Java |
|---|---|---|---|
| Dependencies | go.mod | package.json | pom.xml |
| Autogen dependency | go.sum | package-lock.json |
1 Quick Summary
{go package 1, go package 2} \(\in\) Go module
go packages are .go files
go module is the directory holding the .go files
- The reference name of go packages are declared inside the go file but typically we use the same reference name as the file name.
- Go packages do not import other Go packages, Go packages CAN ONLY IMPORT DIRECTORIES containing Go packages
import( "~/playGO/component" )will import the Directory component and All the *.go packages inside the component directory
When calling functions from imported go packages remember:
Lowercase function name is package-public
Uppercase function name is package-private
2 Go module
2.1 go.mod: Init root dir
mkdir projectFolder
cd projectFolder
go mod init github.com/UserJY/playGOThis will autogenerate go.mod file
github.com/UserJY/playGOis the name and the root directory of our module
2.2 go.sum: Download dependencies
go get -u github.com/gin-gonic/ginThis will autogenerate go.sum file
2.3 Explore go.mod go.sum
module github.com/UserJY/playGO
go 1.16
require (
github.com/gin-gonic/gin v1.7.7 // indirect
...
gopkg.in/yaml.v2 v2.4.0 // indirect
)// indirect means your go project is not using the dependency.
go mod tidy after using the dependency to tidy it up.
github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
g
gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
...go.sum is just the transitive closure of dependencies.
Analogous to package.lock.json
3 Packages
3.1 main.go component/bleh.go
package main
import (
"fmt"
"github.com/UserJY/playGO/component"
//we import the DIRECTORY "component"
//we do not import bleh.go or duhr
)
func main(){
fmt.Println(duhr.Somefunc())
}mkdir component Create component directory
package duhr
func Somefunc() int { // "S" in Somefunc() MUST BE CAPITALIZED
return 2
}“S” in Somefunc() MUST BE CAPITALIZED since it is package-public
This allows main.go to use Somefunc()
duhr.somefunc() WILL FAIL since it is lowercase package-private
4 Running
try below (will fail because we are running locally)
go run .
# main.go:5:2: no required module provides package github.com/UserJY/playGO/bleh; to add it:
# go get github.com/UserJY/playGO/blehTo run locally:
go mod edit -replace github.com/UserJY/playGO/component=~/playGO/componentthis will add replace github.com/UserJY/playGO/component => ~/playGO/component to your go.mod file
