mingw: Resolve path issue, make gopls work on CYGWIN/MSYS2/GitBash (:GoDoc, :GoInfo and :GoDef)

autoload/go/def.vim

@@ -124,8 +124,15 @@ function! go#def#jump_to_declaration(out, mode, bin_name) abort
 
   " strip line ending
   let out = split(final_out, go#util#LineEnding())[0]
+
   if go#util#IsWin()
     let parts = split(out, '\(^[a-zA-Z]\)\@<!:')
+  elseif has('win32unix')
+    " remove comma in cygwin path e.g. '/c:/path'
+    if l:out[0:8] != '/cygdrive' && l:out[2:3] is# ':/'
+      let l:out = l:out[0:1] . l:out[3:]
+    endif
+    let parts = split(out, ':')
   else
     let parts = split(out, ':')
   endif

autoload/go/lsp.vim

@@ -616,13 +616,27 @@ function! s:definitionHandler(next, msg) abort dict
   " gopls returns a []Location; just take the first one.
   let l:msg = a:msg[0]
 
-  let l:line = s:lineinfile(go#path#FromURI(l:msg.uri), l:msg.range.start.line+1)
+  let l:msguri = go#path#FromURI(l:msg.uri)
+
+  if has('win32unix')
+    " remove comma in cygwin path e.g. '/c:/path'
+    if l:msguri[2:3] is# ':/'
+      let l:msguri = l:msguri[0:1] . l:msguri[3:]
+    endif
+
+    " add 'cygdrive' for CYGWIN rather than MSYS2/GitBash
+    if system('uname') =~ 'CYGWIN'
+      let l:msguri = '/cygdrive' . l:msguri
+    endif
+  endif
+
+  let l:line = s:lineinfile(l:msguri, l:msg.range.start.line+1)
   if l:line is -1
     call go#util#EchoWarning('could not find definition')
     return
   endif
 
-  let l:args = [[printf('%s:%d:%d: %s', go#path#FromURI(l:msg.uri), l:msg.range.start.line+1, go#lsp#lsp#PositionOf(l:line, l:msg.range.start.character), 'lsp does not supply a description')]]
+  let l:args = [[printf('%s:%d:%d: %s', l:msguri, l:msg.range.start.line+1, go#lsp#lsp#PositionOf(l:line, l:msg.range.start.character), 'lsp does not supply a description')]]
   call call(a:next, l:args)
 endfunction
 

autoload/go/path.vim

@@ -164,6 +164,15 @@ function! go#path#ToURI(path)
     let l:absolute = 1
     let l:prefix = '/' . l:path[0:1]
     let l:path = l:path[2:]
+  elseif has('win32unix')
+    let l:absolute = 1
+    if l:path[0:8] == '/cygdrive'
+      let l:prefix = l:path[9:10] . ':'
+      let l:path = l:path[11:]
+    else
+      let l:prefix = l:path[0:1] . ':'
+      let l:path = l:path[2:3] is# ':/' ? l:path[3:] : l:path[2:]
+    endif
   endif
 
   return substitute(