flake,ci: reenable GOPROXY var default

...mainly due to arbitrarily failing ci builds, as this doesn't appear
to affect local builds/nix builds on remote builders, just fresh builds
in the ci.
the explanation for why this is happening might be that certain package
VCS's don't allow many/frequent connections from IP ranges other than
GOPROXY's (Google's).
that is sheer speculation, though.
however, it is still true that there are "no" failed ci builds with
GOPROXY env var set to its default value (left untouched), which does
indeed indicate that the above mentioned might be the root cause of the
issue after all.

this commit reverts:
    * f3e481395e
and partially reverts:
    * 14ba7b18bf

GOPROXY=direct has been kept for `nix-shell`/`nix develop` environments
as that is not where it poses an issue.

.drone.starlark

@@ -7,9 +7,6 @@ def main(ctx):
 			"kind": "pipeline",
 			"type": "docker",
 			"name": "golangci-lint",
-			"environment": {
-				"GOPROXY": "direct"
-			},
 			"steps": [
 				{
 					"name": "golangci-lint",
@@ -33,9 +30,6 @@ def main(ctx):
 			"node": {
 				"r": "w"
 			},
-			"environment": {
-				"GOPROXY": "direct"
-			},
 			"steps": [
 				{
 					"name": "pull nix",
@@ -282,9 +276,6 @@ def main(ctx):
 			"node": {
 				"r": "w"
 			},
-			"environment": {
-				"GOPROXY": "direct"
-			},
 			"steps": [
 				{
 					"name": "pull archlinux",
@@ -362,9 +353,6 @@ def main(ctx):
 			"node": {
 				"r": "w"
 			},
-			"environment": {
-				"GOPROXY": "direct"
-			},
 			"steps": [
 				{
 					"name": "pull fedora",

flake.nix

@@ -77,7 +77,7 @@
             nativeBuildInputs = [ pkgconfig ];
 
             overrideModAttrs = _: {
-              GOPROXY = "direct";
+              # GOPROXY = "direct";
             };
 
             inherit version;
@@ -93,7 +93,7 @@
 
             modSha256 = lib.fakeSha256;
             # dont't forget to update vendorSha256 whenever go.mod or go.sum change
-            vendorSha256 = "sha256-gaIoacCs0PcvmFW8dQOFUb9KU1u6KUiFmGQ/ERcVwjc=";
+            vendorSha256 = "sha256-LvdcTbj8cFlaIBsq1VLfLF2Tu9HiZzGO8igD766nMLE=";
 
             # In 'nix develop', we don't need a copy of the source tree
             # in the Nix store.