Bump minimum compiler version from Go 1.15 to 1.18 (#1246)

go.mod

@@ -14,7 +14,7 @@ module github.com/johnkerl/miller
 // Local development:
 // replace github.com/johnkerl/lumin => /Users/kerl/git/johnkerl/lumin
 
-go 1.15
+go 1.18
 
 require (
 	github.com/facette/natsort v0.0.0-20181210072756-2cd4dd1e2dcb
@@ -28,3 +28,12 @@ require (
 	golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab
 	golang.org/x/term v0.0.0-20210927222741-03fcf44c2211
 )
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/felixge/fgprof v0.9.3 // indirect
+	github.com/google/pprof v0.0.0-20211214055906-6f57359322fd // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -37,7 +37,6 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
 github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211007075335-d3039528d8ac/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab h1:2QkjZIsXupsJbJIdSjjUOgWK3aEtzyuh2mPt3l/CkeU=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=