Wrong path on valid requests when error handler exists

[avivpxi]

When i register an error handler to a server instance, whenever i peeks into ctx.Path() method, it seem to corrupt the value of another request which gets handled later on.
I'm building my server with github.com/valyala/fasthttp v1.2.0,
and able to reproduce the issue using this hello world example:

package main

import (
	"fmt"
	"github.com/valyala/fasthttp"
)

func main() {
	server := &fasthttp.Server{
		Handler: requestHandler,
		ErrorHandler: errorHandler,
		MaxRequestBodySize: 10,
		Concurrency: 1,
	}
	if err := server.ListenAndServe(":8080"); err != nil {
		fmt.Println(err)
	}
}

func requestHandler(ctx *fasthttp.RequestCtx) {
	fmt.Printf("handler requested resource: %v %v\n", string(ctx.Method()), string(ctx.Path()))
	fmt.Fprintf(ctx, "Hello, world\n")
}

func errorHandler(ctx *fasthttp.RequestCtx, err error) {
	fmt.Printf("error requested resource: %v %v\n", string(ctx.Method()), string(ctx.Path()))
	fmt.Println("error handler", err)
}

Note that i use MaxRequestBodySize to be able to trigger the error handler using the sent body size, and also note the concurrency parameter (which causes the issue to appear faster).

Now these are the steps to reproduce the issue:

curl -XPOST http://localhost:8080/a -d 'valid body' -> handler requested resource: POST /a
curl -XPOST http://localhost:8080/b -d 'invalid body' -> error requested resource: POST /b
curl -XPOST http://localhost:8080/c -d 'invalid body' -> error requested resource: POST /c
curl -XPOST http://localhost:8080/d -d 'valid body' -> handler requested resource: POST /c

Note that this result is non-deterministic, the last request can also result in handler requested resource: POST /b, but the value was inaccurate every time i tried these steps.

[kirillDanshin]

@avivpxi thanks for pointing out. #551 fixes this issue

[lxj15398019970]

i think this bug is still exist in v 1.50