为什么杜松子酒（golang）使我的自定义标头变成小写？

Question

I'm stuck on this problem while learning go/gin. When I use custom header gin makes it lowercase, here is code example:

package main

import "github.com/gin-gonic/gin"

func main() {
    r := gin.New()
    r.GET("/ping", func(c *gin.Context) {
        c.Header("X-Next", "abc")
        c.String(200, "ok")
    })
    r.Run(":9000")
}

Header becomes x-next, can't figure it out why it is happening. Similar example with standard http module works fine.

Answer 1

Looks like its browser changes case of header, and it is not an issue with gin. Thanks @elithrar for hint.