Update Go

* Enable dependabot monthly updates.
* Update Go minimum to 1.19.
* Update Go modules.

Signed-off-by: SuperQ <superq@gmail.com>

.github/dependabot.yml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      interval: "monthly"
+  - package-ecosystem: "gomod"
+    directory: "/examples/middleware"
+    schedule:
+      interval: "monthly"
+  - package-ecosystem: "gomod"
+    directory: "/tutorial/whatsup"
+    schedule:
+      interval: "monthly"

go.mod

@@ -1,5 +1,5 @@
 module github.com/prometheus/client_model
 
-go 1.18
+go 1.19
 
-require google.golang.org/protobuf v1.30.0
+require google.golang.org/protobuf v1.31.0

go.sum

@@ -4,5 +4,5 @@ github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
-google.golang.org/protobuf v1.30.0 h1:kPPoIgf3TsEvrm0PFe15JQ+570QVxYzEvvHqChK+cng=
-google.golang.org/protobuf v1.30.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
+google.golang.org/protobuf v1.31.0 h1:g0LDEJHgrBl9N9r17Ru3sqWhkIx2NB67okBHPwC7hs8=
+google.golang.org/protobuf v1.31.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=