cmd/govim: add test for racey cmd/go updates per golang.org/issues/37…

…164 (#742)

Test the racing of gopls' usages of go/packages which result in racey usages of
cmd/go modifying go.mod. More detail in:

    golang/go#36772 (comment)

and preceding comments. The test below is an exact copy of the setup that triggered
this failure. The go.mod is intentially "dirty" such that any calls to cmd/go
will cause the require directive to be added. One such call happens in the initial
workspace load, the other is triggered by GOVIMGoToDef if the initial call has not
yet completed. Hence the two race to update go.mod

.github/workflows/test.yml

@@ -26,6 +26,7 @@ env:
   GH_USER: "x-access-token"
   GH_TOKEN: ${{ github.token }}
   GOVIM_TEST_RACE_SLOWDOWN: "1.5"
+  RACE_BUILD: "742"
 
 name: Go
 jobs:

cmd/govim/testdata/scenario_bugs/bug_gopls_37164.txt

@@ -0,0 +1,60 @@
+# Test the racing of gopls' usages of go/packages which result in racey usages of
+# cmd/go modifying go.mod. More detail in:
+#
+#   https://github.com/golang/go/issues/36772#issuecomment-578933218
+#
+# and preceding comments. The test below is an exact copy of the setup that triggered
+# this failure. The go.mod is intentially "dirty" such that any calls to cmd/go
+# will cause the require directive to be added. One such call happens in the initial
+# workspace load, the other is triggered by GOVIMGoToDef if the initial call has not
+# yet completed. Hence the two race to update go.mod
+
+[golang.org/issues/37164] skip
+[short] skip 'Skip short because we sleep for GOVIM_ERRLOGMATCH_WAIT to ensure we don''t have any errors'
+
+vim ex 'e '$WORK/p.go
+vim ex 'call cursor(5,17)'
+vim ex 'GOVIMGoToDef'
+sleep $GOVIM_ERRLOGMATCH_WAIT
+
+# Ensure go.mod has changed as we expect
+cmp go.mod go.mod.golden
+
+# Use our own custom error check
+# noerrcheck
+errlogmatch -start -count=0 'LogMessage callback: &protocol\.LogMessageParams\{Type:(1|2), Message:".*'
+
+-- go.mod --
+module mod.com/p
+
+go 1.12
+
+replace mod.com/q => ./q
+
+-- go.mod.golden --
+module mod.com/p
+
+go 1.12
+
+replace mod.com/q => ./q
+
+require mod.com/q v0.0.0-00010101000000-000000000000
+-- p.go --
+package p
+
+import "mod.com/q"
+
+const Name1 = q.Name
+const Name2 = SameFile
+
+const SameFile = "samefile"
+
+-- q/go.mod --
+module mod.com/q
+
+go 1.12
+
+-- q/q.go --
+package q
+
+const Name = "package q"

internal/cmd/genconfig/genconfig.go

@@ -270,6 +270,7 @@ env:
   GH_USER: "x-access-token"
   GH_TOKEN: ${{ github.token }}
   GOVIM_TEST_RACE_SLOWDOWN: "1.5"
+  RACE_BUILD: "742"
 
 name: Go
 jobs: