or

The falsy values are false, 0, any nil pointer or interface value, any array, slice, map, or string of length zero, and zero time.Time values.

Everything else is truthy.

{{ or 0 1 2 }} → 1
{{ or false "a" 1 }} → a
{{ or 0 true "a" }} → true

{{ or false "" 0 }} → 0
{{ or 0 "" false }} → false

See Go’s text/template documentation for more information.