Failed to install service pack for unknown certification authority

I am trying to install the Go module from bitbucket like this:

go get bitbucket.org/kardianos/osext

      

        
        
        
      

    

But I am getting the following error:

package bitbucket.org/kardianos/osext: Get https://api.bitbucket.org/1.0/repositories/kardianos/osext : x509: certificate signed by an unknown user

Google led me to the instructions for this post , after which I edited /etc/mercurial/hgrc

to contain:

[web]
cacerts = /etc/ssl/certs/ca-certificates.crt

      

        
        
        
      

    

as stated for my OS (Debian), however I still get the same error.

what else can i do?