affected/package:

[Beaelf]

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

$ go version
go version go1.16.3 darwin/amd64

Does this issue reproduce with the latest release?

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

go env Output

$ go env
GO111MODULE="auto"
GOARCH="amd64"
GOBIN="/Users/cd.l/go/bin"
GOCACHE="/Users/cd.l/Library/Caches/go-build"
GOENV="/Users/cd.l/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/cd.l/go/pkg/mod"
GONOPROXY=""
GONOSUMDB="github.com/***/*"
GOOS="darwin"
GOPATH="/Users/cd.l/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.16.3"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/cd.l/Documents/workspace/***/***/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/0n/g4x9qh0n6vb9zp0_06b0hsqr0000gn/T/go-build3173792104=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

go test -v -race ./...

What did you expect to see?

run my test cases

What did you see instead?

[ALTree]

Looks like #49138. Please update to the latest 1.16 minor release, it should be fixed there.

Also please don't post screenshots of text, they make it much harder to search the issues database. A textual search for "unknown class" will not find this issue, because you put the error inside an image.