Go: net/http: NewRequest panics when given a nil instance of *strings.Reader

[xaanit]

What version of Go are you using (go version)?

$ go version
go version go1.13.7 windows/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env

set GO111MODULE=

set GOARCH=amd64

set GOBIN=

set GOCACHE=C:\Users\Jacob\AppData\Local\go-build

set GOENV=C:\Users\Jacob\AppData\Roaming\go\env

set GOEXE=.exe

set GOFLAGS=

set GOHOSTARCH=amd64

set GOHOSTOS=windows

set GONOPROXY=

set GONOSUMDB=

set GOOS=windows

set GOPATH=C:\Users\Jacob\go

set GOPRIVATE=

set GOPROXY=https://proxy.golang.org,direct

set GOROOT=D:\Go

set GOSUMDB=sum.golang.org

set GOTMPDIR=

set GOTOOLDIR=D:\Go\pkg\toolwindows_amd64

set GCCGO=gccgo

set AR=ar

set CC=gcc

set CXX=g++

set CGO_ENABLED=1

set GOMOD=

set CGO_CFLAGS=-g -O2

set CGO_CPPFLAGS=

set CGO_CXXFLAGS=-g -O2

set CGO_FFLAGS=-g -O2

set CGO_LDFLAGS=-g -O2

set PKG_CONFIG=pkg-config

set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\Jacob\AppData\Local\Temp\go-build483288042=/tmp/go-build -gno-record-gcc-switches

What did you do?

Playground: https://play.golang.org/p/5DED9DdFmld
Code in-case playground doesn't work:

package main

import (
    "fmt"
    "net/http"
    "os"
    "strings"
)

func succeeds() {
    _, err := http.NewRequest(http.MethodGet, "", nil)
    if err != nil {
        fmt.Printf("Err from succeeds: %+v\n", err)
        os.Exit(0)
    }
}

func fails() {
    var reader *strings.Reader = nil
    _, err := http.NewRequest(http.MethodGet, "", reader)
    if err != nil {
        fmt.Printf("Err from fails: %+v\n", err)
        os.Exit(0)
    }
}

func main() {
    defer func() {
        if x := recover(); x != nil {
            if err, ok := x.(error); ok {
                fmt.Printf("Err from defer: %+v\n", err)
                panic(err)
            } else {
                panic(x)
            }
        }
    }()
    succeeds()
    fmt.Println("after suceeds")
    fails()
    fmt.Println("after fails")
}

What did you expect to see?

It to work, as GET requests wouldn't have bodies.

What did you see instead?

A panic as it tries to, assumedly, execute this line:

        case *strings.Reader:
            req.ContentLength = int64(v.Len())

[mdlayher]

I don't think there's anything to be done here. Passing a nil *strings.Reader is a clear programming error as noted by the nil pointer dereference panic, regardless of the HTTP method.

[xaanit]

Then why does passing nil directly not throw the same panic? If you shouldn't be passing nil at all that is fine, but the behaviour is inconsistent.

[seankhliao]

https://golang.org/doc/faq#nil_error

[ianlancetaylor]

Closing because this does not seem to be a bug. Please comment if you disagree.