context.Next()

[achempak-polymer]

The docs say that examples using next should be present in this repo (https://pkg.go.dev/github.com/gin-gonic/gin#Context.Next). I'm a bit confused on the lifecycle of middleware. For example, say we have the following middleware:

func timerMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		t1 := time.Now()
		c.Next()
                t2 := time.Now().Sub(t1)
                c.Header("time", t2.Seconds())
	}
}

My goal here is to include the time it took to process the request as a response header. Is the above correct way of doing this?

[FarmerChillax]

This is incorrect, the header has been written to the http response stream in the render method

[SteveFromAccounting]

I had some trouble finding the example documentation in Github like the comment stated, but the documentation here on the gin-gonic website seemed to do an ok job. As I understand it, the lifecycle for middleware focusing on just the usage of context.Next() is:

1. Request comes in
2. Your middleware is hit
3. context.Next() tells gin to short-circuit your middleware logic and go to the next middleware in the chain
4. the response is sent out
5. The logic after context.Next() is now run. Which is why in the example, the only thing that can be done is to log out how long it took to create the response. And you can't actually send out that value in the response itself.