Do not override the deployment target that MacPorts sets.
--- set_goenv.sh.orig	2021-07-12 18:46:40.000000000 -0500
+++ set_goenv.sh	2021-07-12 21:11:26.000000000 -0500
@@ -27,8 +27,6 @@
             export GOCACHE="C:/windows/temp"
             ;;
         Darwin)
-            export CGO_CFLAGS="-mmacosx-version-min=10.11"
-            export CGO_LDFLAGS="-mmacosx-version-min=10.11"
             ;;
     esac