How can I pass a var between routes funcs and change it in every controller?

问题

I want to pass var and change it globally in every controller between routes so if controller1 change var to "as" I want controller2 to use the new value of the var = "as". How can I do it? something like this

main.go:

var test []string

func NewRouter() *gin.Engine {
    gin.SetMode(gin.ReleaseMode)
    r := gin.New()
    r.GET("/ping", gets(test))
    r.Run(":6030")
    return r
}

controller.go:

func gets(test) gin.HandlerFunc {
   fn := func(c *gin.Context){
               // Here I want to change my var (test) and I want to change it globally so if any another function use it I want to use the new value I just change it here
         }
}

回答1:

The comment of mkopriva already give you a solution on how to using mutex.

However, since golang promote share memory by communicating, I propose another solution using channel.

package main

import (
    "fmt"
    "github.com/gin-gonic/gin"
)

func main() {
  r := NewRouter()
  r.Run(":6030")
}

var test = []string{"abc"}

func NewRouter() *gin.Engine {
    gin.SetMode(gin.ReleaseMode)
    r := gin.New()

    updateChan := make(chan []string, 0)
    r.GET("/", gets(updateChan))
    r.GET("/mn", er(updateChan))
    return r
}

func gets(updateChan chan []string) gin.HandlerFunc {
    return func(c *gin.Context){
        fmt.Println("before update in get, test=",test)
        newTest := []string{"def"}
        updateChan <- newTest
  }

}

func er(updateChan chan []string) gin.HandlerFunc {
    return func(c *gin.Context){
        test = <-updateChan
        fmt.Println("get a new value for test in er, test=",test)

  }

}

With an unbuffered channel updateChan, test will always be update with the latest input pushed to updateChan channel. And no data race will happen here.

Of course this is just a simple demonstration and there are lot more stuff to make a complete HTTP server with gin. But I limit the scope of the demonstration to channel usage only.

来源：https://stackoverflow.com/questions/61968405/how-can-i-pass-a-var-between-routes-funcs-and-change-it-in-every-controller

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gin-gonic