Update minimum Go version to 1.19

On Go 1.18 since a5ebe22, we get:

    # github.com/docker/docker-credential-helpers/client
    vendor/github.com/docker/docker-credential-helpers/client/command.go:34:39: programCmd.Environ undefined (type *exec.Cmd has no field or method Environ)
    note: module requires Go 1.19
    # github.com/docker/cli/cli/connhelper/commandconn
    cli/connhelper/commandconn/commandconn.go:71:22: undefined: atomic.Bool
    cli/connhelper/commandconn/commandconn.go:76:22: undefined: atomic.Bool
    cli/connhelper/commandconn/commandconn.go:77:22: undefined: atomic.Bool
    cli/connhelper/commandconn/commandconn.go:78:22: undefined: atomic.Bool

These go away when building against 1.19+.

Signed-off-by: Tianon Gravi <admwiggin@gmail.com>

scripts/vendor

@@ -18,12 +18,12 @@ init() {
   cat > go.mod <<EOL
 module github.com/docker/cli
 
-go 1.18
+go 1.19
 EOL
 }
 
 update() {
-  (set -x ; go mod tidy -compat=1.18 -modfile=vendor.mod; go mod vendor -modfile=vendor.mod)
+  (set -x ; go mod tidy -compat=1.19 -modfile=vendor.mod; go mod vendor -modfile=vendor.mod)
 }
 
 validate() {

vendor.mod

@@ -4,7 +4,7 @@ module github.com/docker/cli
 // There is no 'go.mod' file, as that would imply opting in for all the rules
 // around SemVer, which this repo cannot abide by as it uses CalVer.
 
-go 1.18
+go 1.19
 
 require (
 	dario.cat/mergo v1.0.0