go.mod: upgrade to go 1.17

This change was produced using 'go mod tidy -go=1.17'
with a go command built at CL 315210.

This activates lazy loading, and updates the go.mod file to maintain
the lazy-loading invariants (namely, including an explicit requirement
for every package transitively imported by the main module).

Note that this does *not* prevent users with earlier go versions from
successfully building packages from this module.

For golang/go#36460

Change-Id: Iabb65fc3ed9727abecc3926abcecd445c967d0a9
Reviewed-on: https://go-review.googlesource.com/c/text/+/315571
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/go.mod b/go.mod
index 8ff7ecb..63bc05f 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@
 require golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e
-go 1.11
+go 1.17