What version of golang is currently used to compile geth? Look at 1.15 used by go.mod, but some unit test compilation fails

[cppfuns]

What version of golang is currently used to compile geth? Look at 1.15 used by go.mod, but some unit test compilation fails

go-ethereum/go.mod

Line 3 in 356bbe3

go 1.15

surou@bcskill_com go-ethereum % go test -v ./internal/cmdtest/test_cmd.go
go: downloading gotest.tools v2.2.0+incompatible
# command-line-arguments
internal/cmdtest/test_cmd.go:124:39: undefined: io.ReadAll

golang/go#44568

[ligi]

1.16 and 1.17 are used - see https://github.com/ethereum/go-ethereum/blob/master/.travis.yml

[marshalys]

why go.mod version not change to 1.16 or 1.17?