SSH tunnel fails: "ssh: must specify HostKeyCallback"

[danielstandby]

This is what I did:

1. Installed go and tern
2. Configured a tern.conf file with [database] and [ssh-tunnel] entries
3. Added SSH private key to ssh-agent
4. Created a dummy migration file
5. Tried to execute tern migrate but got the following error:

Unable to connect to PostgreSQL:
  ssh: must specify HostKeyCallback

Seems that from version 1.8.3, Go made some braking changes on SSL connections: golang/go#19767

[Jack Christensen]

I made a small change to use the user's known_hosts file if possible.