Here's a shell command that will list all available Go versions similar to the output of rbenv install -l or nvm ls-remote:

wget -q -O- golang.org/dl | sed -n -E 's/.*toggle(Visible)?" id="(go.*)">/\2/p' | sort | uniq

Running it gives the following output:

$ wget -q -O- golang.org/dl | sed -n -E 's/.*toggle(Visible)?" id="(go.*)">/\2/p' | sort | uniq
go1
go1.10
go1.10.1
go1.10.2
go1.10.3
go1.10.4
go1.10.5
go1.10.6
go1.10.7
go1.11
go1.11.1
go1.11.2
go1.11.3
go1.11.4
go1.12beta1
go1.2.2
go1.3
go1.3.1
go1.3.2
go1.3.3
go1.4
go1.4.1
go1.4.2
go1.4.3
go1.5
go1.5.1
go1.5.2
go1.5.3
go1.5.4
go1.6
go1.6.1
go1.6.2
go1.6.3
go1.6.4
go1.7
go1.7.1
go1.7.3
go1.7.4
go1.7.5
go1.7.6
go1.8
go1.8.1
go1.8.2
go1.8.3
go1.8.4
go1.8.5
go1.8.6
go1.8.7
go1.9
go1.9.1
go1.9.2
go1.9.3
go1.9.4
go1.9.5
go1.9.6
go1.9.7
$  

It works because the Downloads page at the Go website has a pretty regular structure—each version has its own <div> block which happens to follow a specific pattern, either

<div class="toggleVisible" id="go1.11.4">

or

<div class="toggle" id="go1.12beta1">

Knowing this, it's easy to extract the version number with a regular expression. I used something the following:

class="toggle(Visible)?" id="(go.+)"

And the adapted it to work with sed:

sed -n -E 's/.*toggle(Visible)?" id="(go.*)">/\2/p'

The .* at the front matches the entire line, replaces it with the content of the second capturing group (\2) and prints it (the p at the end). The -n flag tells sed to only print the matching lines, while -E uses regular expressions rather than basic regular expressions¹.

wget is used to download the content of the page at https://golang.org/dl/, but another command like curl or a file could have been used as input instead.

sort and uniq are just there to remove any duplicate entries, since right now go1.12beta1 appears twice in the HTML.

Final note

I understand that in general we shouldn't parse HTML with regex, but I̛ gues̛s i̘̘̯̱͜t̯̬̤̬̗̬ ̫̬̼͖͎̣w̸o̺̩͇͚͚͇rk͓͓͓͎̱ͅs̵͔̣͕͕͙ t͉͕̭͈͉̣͝ͅḫ̢̜̗͎́i̸̝̮͉̠̲͔͢s͔̖͔̗̗̯̝̖ ̩̞̫͙t̸̠i͎̕m͉̖͢͜e̵̹̜͓̼͉̞͇.