Switch to Go modules, update dependencies

vendor/golang.org/x/sys/windows/env_windows.go

@@ -8,7 +8,6 @@ package windows
 
 import (
 	"syscall"
-	"unicode/utf16"
 	"unsafe"
 )
 
@@ -40,17 +39,11 @@ func (token Token) Environ(inheritExisting bool) (env []string, err error) {
 	defer DestroyEnvironmentBlock(block)
 	blockp := uintptr(unsafe.Pointer(block))
 	for {
-		entry := (*[(1 << 30) - 1]uint16)(unsafe.Pointer(blockp))[:]
-		for i, v := range entry {
-			if v == 0 {
-				entry = entry[:i]
-				break
-			}
-		}
+		entry := UTF16PtrToString((*uint16)(unsafe.Pointer(blockp)))
 		if len(entry) == 0 {
 			break
 		}
-		env = append(env, string(utf16.Decode(entry)))
+		env = append(env, entry)
 		blockp += 2 * (uintptr(len(entry)) + 1)
 	}
 	return env, nil