build: deprecate Ubuntu Cosmic, start supporting Eoan

build/ci.go

@@ -137,7 +137,8 @@ var (
 	// Note: yakkety is unsupported because it was officially deprecated on Launchpad.
 	// Note: zesty is unsupported because it was officially deprecated on Launchpad.
 	// Note: artful is unsupported because it was officially deprecated on Launchpad.
-	debDistros = []string{"trusty", "xenial", "bionic", "cosmic", "disco"}
+	// Note: cosmic is unsupported because it was officially deprecated on Launchpad.
+	debDistros = []string{"trusty", "xenial", "bionic", "disco", "eoan"}
 )
 
 var GOBIN, _ = filepath.Abs(filepath.Join("build", "bin"))