Make Gin run on some other port

I have this in my main.go file

package main

import (
	"github.com/gin-gonic/gin"
	"github.com/someone/something/backend/config"
)

func main() {

	app := config.App()

	env := app.Env
	gin := gin.Default()
	
	gin.Run(":" + env.PORT)
}

Where PORT is 8080.

When I run go run main.go it says Listening and serving HTTP on :8080

but when I run gin run main.go it says Listening on port 3000

How can I change port here? to something else. I need to run something else on port 3000

Update: gin run main.go --port 8080 still logs Listening on port 3000.

Update: 2 gin run --port 8080 main.go also says listening on port 3000

Update: 3 GIN_MODE=debug PORT=8080 gin run main.go also doesn't work.

The gin command is related to a different repository github.com/codegangsta/gin.

The GIN_MODE environment variable has no effect on the gin command because it is not related with it. Also changing default port value of it with PORT environment variable won't work, because it relies on -p,--port flags or GIN_PORT environment variable to change the default port value of itself.

If you want to change the default value of port for gin command you can use either of these options:

Use the --port or -p flag following the proper syntax
or;
Using the environment variable GIN_PORT with the desired port as the value (GIN_PORT=8080)

When using the -p or --port flag, the command syntax is strict and this must be placed before the command run

example: gin -p 8080 run main.go or gin --port 8080 run main.go

NOTE: Your previous attempts to use --port did not have any effect because it was not placed properly in the command's syntax, between gin and run

To change the port using variables:

First, set the variable, such as export GIN_PORT=8080 and then running the command gin run main.go (you can do this in one command using export GIN_PORT=8080 && gin run main.go)

The difference between setting the port via environment variable and setting port with flags is that if you set port with export GIN_PORT=value, the program will use this port in place of the program default unless the -p or --port flag is used explicitly with the command, which will override the environment variable.

If you set port with flags, the port will only be changed for that single instance.

Of course you can set GIN_PORT in any file you use to set variables with, so that you don't have to set this each time you log in.

Additional Information

The cli.IntFlag struct initialization located on lines 48-53 in the main.go of the gin command:

cli.IntFlag{
			Name:   "port,p",
			Value:  3000,
			EnvVar: "GIN_PORT",
			Usage:  "port for the proxy server",
		},

Defines default port value of the gin command as well as which flags and which environment variable can change it. Name field for the flags. Value field for the default value. EnvVar field for the environment variable.

You can use the environment variable PORT:

 PORT=8080 && gin run main.go

The resolveAddress() function does check the environment variable:

func resolveAddress(addr []string) string {
	switch len(addr) {
	case 0:
		if port := os.Getenv("PORT"); port != "" {
			debugPrint("Environment variable PORT=\"%s\"", port)
			return ":" + port
		}
		debugPrint("Environment variable PORT is undefined. Using port :8080 by default")
		return ":8080"
	case 1:
		return addr[0]
	default:
		panic("too many parameters")
	}
}

That means, in a Linux-like shell, you should be able to do:

PORT=8080 gin run

And you can display more logs with:

GIN_MODE=debug PORT=8080 gin run

Regarding your program (the one with your own main.go), check the name of your project in your go.mod, and try:

cd /path/to/my/project
go install
which yourAPP # should be /Users/RohitB/go/bin/yourApp
GIN_MODE=debug PORT=8080 yourAPP

If you need codegangsta/gin, check with gin --version that you did not install by mistake github.com/gin-gonic/gin.