Introduction

In request processes, some custom set variables are often shared in the context, such as setting some variables through middleware before the request starts, which can then be accessed in the routing service method for corresponding processing. This requirement is very common. In the GoFrame framework, we recommend using the Context context object to handle context variables shared in the process, even passing this object further into various dependent module methods. The Context object type implements the standard library's context.Context API, which is often used as the first parameter of module inter-call methods, and this API parameter is also the recommended way by Golang official to pass context variables between modules.

Method List:

func (r *Request) GetCtx() context.Context
func (r *Request) SetCtx(ctx context.Context)
func (r *Request) GetCtxVar(key interface{}, def ...interface{}) *gvar.Var
func (r *Request) SetCtxVar(key interface{}, value interface{})

Brief Explanation:

1. The GetCtx method is used to get the current context.Context object, serving the same purpose as the Context method.
2. The SetCtx method is used to set a custom context.Context context object.
3. The GetCtxVar method is used to get the context variable and can provide a default value if the variable does not exist.
4. The SetCtxVar method is used to set the context variable.

Usage Example

Example 1, SetCtxVar/GetCtxVar

package main

import (
    "github.com/gogf/gf/v2/frame/g"
    "github.com/gogf/gf/v2/net/ghttp"
)

const (
    TraceIdName = "trace-id"
)

func main() {
    s := g.Server()
    s.Group("/", func(group *ghttp.RouterGroup) {
        group.Middleware(func(r *ghttp.Request) {
            r.SetCtxVar(TraceIdName, "HBm876TFCde435Tgf")
            r.Middleware.Next()
        })
        group.ALL("/", func(r *ghttp.Request) {
            r.Response.Write(r.GetCtxVar(TraceIdName))
        })
    })
    s.SetPort(8199)
    s.Run()
}

As you can see, we can use SetCtxVar and GetCtxVar to set and get custom variables, and the lifecycle of these variables is limited to the current request process.

After execution, access http://127.0.0.1:8199/, and the page output is:

HBm876TFCde435Tgf

Example 2, SetCtx

The SetCtx method is often used in middleware to integrate some third-party components, such as third-party tracing components.

To simplify the example, let's modify the above example using the SetCtx method for demonstration.

package main

import (
    "context"
    "github.com/gogf/gf/v2/frame/g"
    "github.com/gogf/gf/v2/net/ghttp"
)

const (
    TraceIdName = "trace-id"
)

func main() {
    s := g.Server()
    s.Group("/", func(group *ghttp.RouterGroup) {
        group.Middleware(func(r *ghttp.Request) {
            ctx := context.WithValue(r.Context(), TraceIdName, "HBm876TFCde435Tgf")
            r.SetCtx(ctx)
            r.Middleware.Next()
        })
        group.ALL("/", func(r *ghttp.Request) {
            r.Response.Write(r.Context().Value(TraceIdName))
            // Alternatively, you can use
            // r.Response.Write(r.GetCtxVar(TraceIdName))
        })
    })
    s.SetPort(8199)
    s.Run()
}

After execution, access http://127.0.0.1:8199/, and the page output is:

HBm876TFCde435Tgf