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Panic when trying to serve http with embedded assets #43761

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Cookie04DE opened this issue Jan 18, 2021 · 6 comments
Closed

Panic when trying to serve http with embedded assets #43761

Cookie04DE opened this issue Jan 18, 2021 · 6 comments
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@Cookie04DE
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Cookie04DE commented Jan 18, 2021 •
edited by seankhliao
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What version of Go are you using (go version)?

$ go version
go version go1.16beta1 linux/amd64

Does this issue reproduce with the latest release?

Yes.

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

go env 
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/conrad/.cache/go-build"
GOENV="/home/conrad/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/media/conrad/Seagate/Programmieren/Go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/media/conrad/Seagate/Programmieren/Go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/media/conrad/Seagate/Installationen/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/media/conrad/Seagate/Installationen/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build184147953=/tmp/go-build -gno-record-gcc-switches"

What did you do?

package main

import (
	"embed"
	"net/http"
)

//go: embed assets/*
var assets embed.FS

func main() {
	fs := http.FileServer(http.FS(assets))
	http.ListenAndServe(":48784", fs)
}

I created a folder called 'assets' containing only index.html with the following content:

<html>
    <head>
    </head>
    <body>
        <h>Hello World!</h>
    </body>
</html>

I then ran go1.16beta1 run .

What did you expect to see?

No panic and the static site being served on localhost:48784.

What did you see instead?

This panic:

2021/01/18 21:26:57 http: panic serving [::1]:55146: runtime error: invalid memory address or nil pointer dereference
goroutine 6 [running]:
net/http.(*conn).serve.func1(0xc00010e960)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:1824 +0x153
panic(0x663180, 0x84ba30)
        /home/conrad/sdk/go1.16beta1/src/runtime/panic.go:971 +0x47a
embed.FS.readDir(0x0, 0x6a6905, 0x1, 0x84d580, 0x7f12ea36a3a0, 0x0)
        /home/conrad/sdk/go1.16beta1/src/embed/embed.go:266 +0x26
embed.FS.Open(0x0, 0x6a6905, 0x1, 0x8, 0x889f28, 0x44ed8c, 0x203000)
        /home/conrad/sdk/go1.16beta1/src/embed/embed.go:285 +0xce
net/http.ioFS.Open(0x6faa40, 0x0, 0xc000016384, 0x1, 0xc000168000, 0x7f12ea36a3a0, 0xc0001179c0, 0x40f27b)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:760 +0x68
net/http.serveFile(0x6fde30, 0xc0001480e0, 0xc000162000, 0x6fad20, 0xc000012c10, 0xc000016384, 0x1, 0xc000100e01)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:597 +0x84
net/http.(*fileHandler).ServeHTTP(0xc000012c20, 0x6fde30, 0xc0001480e0, 0xc000162000)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:848 +0x9c
net/http.serverHandler.ServeHTTP(0xc000148000, 0x6fde30, 0xc0001480e0, 0xc000162000)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:2887 +0xa3
net/http.(*conn).serve(0xc00010e960, 0x6fe2a0, 0xc000028280)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:1952 +0x8ed
created by net/http.(*Server).Serve
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:3013 +0x39b
2021/01/18 21:26:58 http: panic serving [::1]:55190: runtime error: invalid memory address or nil pointer dereference
goroutine 18 [running]:
net/http.(*conn).serve.func1(0xc000190000)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:1824 +0x153
panic(0x663180, 0x84ba30)
        /home/conrad/sdk/go1.16beta1/src/runtime/panic.go:971 +0x47a
embed.FS.readDir(0x0, 0x6a6905, 0x1, 0x84d580, 0x7f12c1eee538, 0x0)
        /home/conrad/sdk/go1.16beta1/src/embed/embed.go:266 +0x26
embed.FS.Open(0x0, 0x6a6905, 0x1, 0x8, 0x889f28, 0x64, 0x203000)
        /home/conrad/sdk/go1.16beta1/src/embed/embed.go:285 +0xce
net/http.ioFS.Open(0x6faa40, 0x0, 0xc000194024, 0x1, 0x24, 0x7f12c1eee538, 0xc0000509c0, 0x40f27b)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:760 +0x68
net/http.serveFile(0x6fde30, 0xc0001b0000, 0xc00019e000, 0x6fad20, 0xc000012c10, 0xc000194024, 0x1, 0xc00018c001)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:597 +0x84
net/http.(*fileHandler).ServeHTTP(0xc000012c20, 0x6fde30, 0xc0001b0000, 0xc00019e000)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:848 +0x9c
net/http.serverHandler.ServeHTTP(0xc000148000, 0x6fde30, 0xc0001b0000, 0xc00019e000)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:2887 +0xa3
net/http.(*conn).serve(0xc000190000, 0x6fe2a0, 0xc000196000)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:1952 +0x8ed
created by net/http.(*Server).Serve
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:3013 +0x39b
2021/01/18 21:27:03 http: panic serving [::1]:55398: runtime error: invalid memory address or nil pointer dereference
goroutine 8 [running]:
net/http.(*conn).serve.func1(0xc00010ea00)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:1824 +0x153
panic(0x663180, 0x84ba30)
        /home/conrad/sdk/go1.16beta1/src/runtime/panic.go:971 +0x47a
embed.FS.readDir(0x0, 0x6a6905, 0x1, 0x84d580, 0x0, 0x0)
        /home/conrad/sdk/go1.16beta1/src/embed/embed.go:266 +0x26
embed.FS.Open(0x0, 0x6a6905, 0x1, 0x8, 0x7f12ea36a538, 0x90, 0x203000)
        /home/conrad/sdk/go1.16beta1/src/embed/embed.go:285 +0xce
net/http.ioFS.Open(0x6faa40, 0x0, 0xc000016494, 0x1, 0x203000, 0xc0001641b8, 0xc0000559c0, 0x40f27b)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:760 +0x68
net/http.serveFile(0x6fde30, 0xc0001481c0, 0xc000162100, 0x6fad20, 0xc000012c10, 0xc000016494, 0x1, 0xc000101001)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:597 +0x84
net/http.(*fileHandler).ServeHTTP(0xc000012c20, 0x6fde30, 0xc0001481c0, 0xc000162100)
        /home/conrad/sdk/go1.16beta1/src/net/http/fs.go:848 +0x9c
net/http.serverHandler.ServeHTTP(0xc000148000, 0x6fde30, 0xc0001481c0, 0xc000162100)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:2887 +0xa3
net/http.(*conn).serve(0xc00010ea00, 0x6fe2a0, 0xc000028400)
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:1952 +0x8ed
created by net/http.(*Server).Serve
        /home/conrad/sdk/go1.16beta1/src/net/http/server.go:3013 +0x39b
@Cookie04DE Cookie04DE changed the title Panic when trying to server http with embedded assets Panic when trying to serve http with embedded assets Jan 18, 2021
@seankhliao
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//go: embed should not contain a space

@seankhliao
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Unlike many projects, the Go project does not use GitHub Issues for general discussion or asking questions. GitHub Issues are used for tracking bugs and proposals only.

For asking questions, see:

@Cookie04DE
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Thanks, that worked. Perhaps this should produce a more helpful error, this one is a bit cryptic.

@seankhliao
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there's https://go-review.googlesource.com/c/go/+/283852/ for not panicking

@bcmills
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bcmills commented Feb 2, 2021

Duplicate of #43682

@bcmills bcmills marked this as a duplicate of #43682 Feb 2, 2021
@bcmills
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bcmills commented Feb 2, 2021

(See related proposal #43698.)

@golang golang locked and limited conversation to collaborators Feb 2, 2022
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@bcmills @gopherbot @seankhliao @Cookie04DE