How to get full server URL from any endpoint handler in Gin

Question

I'm creating an endpoint using Go's Gin web framework. I need full server URL in my handler function. For example, if server is running on http://localhost:8080 and my endpoint is /foo then I need http://localhost:8080/foo when my handler is called.

If anyone is familiar with Python's fast API, the Request object has a method url_for(<endpoint_name>) which has the exact same functionality: https://stackoverflow.com/a/63682957/5353128

In Go, I've tried accessing context.FullPath() but that only returns my endpoint /foo and not the full URL. Other than this, I can't find appropriate method in docs: https://pkg.go.dev/github.com/gin-gonic/gin#Context

So is this possible via gin.Context object itself or are there other ways as well? I'm completely new to Go.

Do you want to get `http://localhost:8080/foo` from gin context or handle path variable like you mentioned in python example? — nipuna, Aug 18 '21 at 17:01
@nipuna I want to get that base URL from gin context as that's only available object inside my handler function. I don't want to handle path variables. — Kaushal28, Aug 18 '21 at 17:12

Nick · Accepted Answer · 2021-08-18T17:47:28.007

13

c.Request.Host+c.Request.URL.Path should work but the scheme has to be determined.

package main

import (
    "fmt"

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

func main() {
    r := gin.Default()

    r.GET("/foo", func(c *gin.Context) {
        fmt.Println("The URL: ", c.Request.Host+c.Request.URL.Path)
    })

    r.Run(":8080")
}

You can determine scheme which also you may know already. But you can check as follows:

scheme := "http"
if c.Request.TLS != nil {
    scheme = "https"
}

If your server is behind the proxy, you can get the scheme by c.Request.Header.Get("X-Forwarded-Proto")

edited Aug 18 '21 at 17:47

answered Aug 18 '21 at 17:17

Nick

1,017
1
10
16

Related: [Why are request.URL.Host and Scheme blank in the development server?](https://stackoverflow.com/questions/6899069/why-are-request-url-host-and-scheme-blank-in-the-development-server) – blackgreen Aug 18 '21 at 20:30
1

@blackgreen Yes, I noticed that too basically on development server nothing much available on `Request.URL` except `Path`. That is why I think it's safer to user `Request.Host` for host. – Nick Aug 18 '21 at 20:58
Thanks. How did you come up with this? Is it documented? – Kaushal28 Aug 19 '21 at 07:36
1

@Kaushal28 not directly documented, because this depends on the http library, not Gin. See this https://github.com/gin-gonic/gin/issues/1233 – blackgreen Aug 20 '21 at 07:41
1

@Kaushal28 As blackgreen mentioned, it's not documented directly. But you come to know it by experience specifically if you have it with `net/http` library. – Nick Aug 20 '21 at 10:18
Might this not be unsafe? It reads the url _from the request_. From its doc string: "To prevent DNS rebinding attacks, server Handlers should validate that the Host header has a value for which the Handler considers itself authoritative." - The _real_ server url might be different, might it not? – Zsar May 15 '22 at 16:05

nipuna · Answer 2 · 2021-08-18T17:46:21.880

You can get host part localhost:8080 from context.Request.Host and path part /foo from context.Request.URL.String().

package main

import (
    "fmt"
    "net/http"

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

func main() {
    r := gin.Default()
    r.GET("/foo", func(c *gin.Context) {
        c.String(http.StatusOK, "bar")
        fmt.Println(c.Request.Host+c.Request.URL.String())
    })
    // Listen and Server in 0.0.0.0:8080
    r.Run(":8080")
}

And you can get http protocol version by context.Request.Proto, But it will not determine http or https. you need to get it from your service specifications.

How to get full server URL from any endpoint handler in Gin

2 Answers2