upgrade golang to v1.22

general note about defaults

go 1.18

from golang v1.16 --> v1.18

golang.org/x/sys now requires go v1.17 or greater.  It's become too painful to stay on 1.16

go modules update and tidy

fix #493 by upgrading golang.org/x/net

Merge branch 'pr/flexponsive/481'

fix #492 build under go 1.16 by forcing use of go.uber.org/[email protected]

Merge branch 'pr/apanzerj/444'

#439 honor DocumentRoot for error pages