add sync/errgroup like functionality (#28)
add sync/errgroup like functionality
diff --git a/group.go b/group.go
new file mode 100644
index 0000000..9c29efb
--- /dev/null
+++ b/group.go
@@ -0,0 +1,38 @@
+package multierror
+
+import "sync"
+
+// Group is a collection of goroutines which return errors that need to be
+// coalesced.
+type Group struct {
+ mutex sync.Mutex
+ err *Error
+ wg sync.WaitGroup
+}
+
+// Go calls the given function in a new goroutine.
+//
+// If the function returns an error it is added to the group multierror which
+// is returned by Wait.
+func (g *Group) Go(f func() error) {
+ g.wg.Add(1)
+
+ go func() {
+ defer g.wg.Done()
+
+ if err := f(); err != nil {
+ g.mutex.Lock()
+ g.err = Append(g.err, err)
+ g.mutex.Unlock()
+ }
+ }()
+}
+
+// Wait blocks until all function calls from the Go method have returned, then
+// returns the multierror.
+func (g *Group) Wait() *Error {
+ g.wg.Wait()
+ g.mutex.Lock()
+ defer g.mutex.Unlock()
+ return g.err
+}
diff --git a/group_test.go b/group_test.go
new file mode 100644
index 0000000..9d472fd
--- /dev/null
+++ b/group_test.go
@@ -0,0 +1,44 @@
+package multierror
+
+import (
+ "errors"
+ "strings"
+ "testing"
+)
+
+func TestGroup(t *testing.T) {
+ err1 := errors.New("group_test: 1")
+ err2 := errors.New("group_test: 2")
+
+ cases := []struct {
+ errs []error
+ nilResult bool
+ }{
+ {errs: []error{}, nilResult: true},
+ {errs: []error{nil}, nilResult: true},
+ {errs: []error{err1}},
+ {errs: []error{err1, nil}},
+ {errs: []error{err1, nil, err2}},
+ }
+
+ for _, tc := range cases {
+ var g Group
+
+ for _, err := range tc.errs {
+ err := err
+ g.Go(func() error { return err })
+
+ }
+
+ gErr := g.Wait()
+ if gErr != nil {
+ for i := range tc.errs {
+ if tc.errs[i] != nil && !strings.Contains(gErr.Error(), tc.errs[i].Error()) {
+ t.Fatalf("expected error to contain %q, actual: %v", tc.errs[i].Error(), gErr)
+ }
+ }
+ } else if !tc.nilResult {
+ t.Fatalf("Group.Wait() should not have returned nil for errs: %v", tc.errs)
+ }
+ }
+}
