env GO111MODULE=on
env GOPROXY=$GOPROXY/invalid

! go list -m rsc.io/quote@latest
stderr '^go: module rsc.io/quote: invalid response from proxy "'$GOPROXY'": invalid character ''i'' looking for beginning of value$'

! go list -m rsc.io/quote@1.5.2
stderr '^go: rsc.io/quote@1.5.2: invalid version: invalid response from proxy "'$GOPROXY'": invalid character ''i'' looking for beginning of value$'