This falls into the category of "complex" as I have no experience with 'go', nor do I have ready access to AIX 7.2 or POWER8 (FYI: I do what I do on personally owned systems, not IBM nor customer systems.)
I assume 'x509' is your hostname.
Did you verify with any of host, nslookup, and/or dig that the hostname is resolveable?
If yes, did you verify that the port number used by go to import (e.g., 80, 443, or maybe something special) is reachable (I use 'telnet host.to.connect.to 443' and hope for a 'connection'.
While, or immediately following your request.
This must fail (as 1.2.3.4 does not exist)
michael@x071:[/home/michael]telnet 1.2.3.4 12345
Trying...
michael@x071:[/home/michael]netstat -tn | grep 12345
tcp 0 0 192.168.2.1.38567 1.2.3.4.12345 SYN_SENT
Another idea to learn more about the error messages - use a wrong hostname, use a wrong package name.
As - it should be working.
Lastly - as I do not know 'go' - what is a possible meaning re: "failed to load system roots and no roots provided"