snapshot of https://github.com/uber-go/guide.git (master, 2026-09-15; blobs > 131072B omitted)

src/error-name.md

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+# Error Naming
+
+For error values stored as global variables,
+use the prefix `Err` or `err` depending on whether they're exported.
+This guidance supersedes the [Prefix Unexported Globals with _](global-name.md).
+
+```go
+var (
+  // The following two errors are exported
+  // so that users of this package can match them
+  // with errors.Is.
+
+  ErrBrokenLink = errors.New("link is broken")
+  ErrCouldNotOpen = errors.New("could not open")
+
+  // This error is not exported because
+  // we don't want to make it part of our public API.
+  // We may still use it inside the package
+  // with errors.Is.
+
+  errNotFound = errors.New("not found")
+)
+```
+
+For custom error types, use the suffix `Error` instead.
+
+```go
+// Similarly, this error is exported
+// so that users of this package can match it
+// with errors.As.
+
+type NotFoundError struct {
+  File string
+}
+
+func (e *NotFoundError) Error() string {
+  return fmt.Sprintf("file %q not found", e.File)
+}
+
+// And this error is not exported because
+// we don't want to make it part of the public API.
+// We can still use it inside the package
+// with errors.As.
+
+type resolveError struct {
+  Path string
+}
+
+func (e *resolveError) Error() string {
+  return fmt.Sprintf("resolve %q", e.Path)
+}
+```