Panic when trying to serve http with embedded assets #43761
Description
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