lib/readers: add NewContextReader to error on context errors

lib/readers/context_test.go

@@ -0,0 +1,28 @@
+package readers
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestContextReader(t *testing.T) {
+	r := NewPatternReader(100)
+	ctx, cancel := context.WithCancel(context.Background())
+	cr := NewContextReader(ctx, r)
+
+	var buf = make([]byte, 3)
+
+	n, err := cr.Read(buf)
+	require.NoError(t, err)
+	assert.Equal(t, 3, n)
+	assert.Equal(t, []byte{0, 1, 2}, buf)
+
+	cancel()
+
+	n, err = cr.Read(buf)
+	assert.Equal(t, context.Canceled, err)
+	assert.Equal(t, 0, n)
+}