错误：“ rsa.PSSOptions”中的未知字段“哈希”

So, I am building docker that uses rsa module of golang. I am using golang by building gcc, which has gccgo.

linux-l853:~/docker # go version
go version gccgo (GCC) 5.0.0 20141113 (experimental) linux/ppc64

Now, when I am building it, I get the following error:

github.com/endophage/gotuf/signed
vendor/src/github.com/endophage/gotuf/signed/verifiers.go:102:50: error: unknown field ‘Hash’ in ‘rsa.PSSOptions’
  opts := rsa.PSSOptions{SaltLength: sha256.Size, Hash: crypto.SHA256}
                                                  ^

Wherein I know that Hash field is defined in rsa.PSSOptions. Any idea why am I getting this error?

TIA.