dl/gotip: gotip panics without arguments

[dvrkps]

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

$ go version devel +2b70ffe Fri May 15 16:15:25 2020 +0000 darwin/amd64

Does this issue reproduce with the latest release?

Sure

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

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/davor/Library/Caches/go-build"
GOENV="/Users/davor/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOOS="darwin"
GOPATH="/Users/davor/go"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/davor/goproject/dl/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 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/9h/yvy5nvq917n_xcbth_j21kkh0000gn/T/go-build689897483=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

a type gotip without any arguments

What did you expect to see?

Standard go command help message.

What did you see instead?

panic: runtime error: index out of range [1] with length 1

goroutine 1 [running]:
main.main()
	/Users/davor/go/pkg/mod/golang.org/dl@v0.0.0-20200514221906-2a7874809c5f/gotip/main.go:40 +0xa65

[gopherbot]

Change https://golang.org/cl/234158 mentions this issue: gotip: fix panic for no arguments