Update dependencies

vendor/github.com/u-root/uio/rand/random.go

@@ -0,0 +1,62 @@
+// Copyright 2019 the u-root Authors. All rights reserved
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package rand implements cancelable reads from a cryptographically safe
+// random number source.
+package rand
+
+import (
+	"context"
+)
+
+// Reader is a cryptographically safe random number source.
+var Reader = DefaultReaderWithContext(context.Background())
+
+// Read blockingly reads from a random number source.
+func Read(b []byte) (int, error) {
+	return Reader.Read(b)
+}
+
+// ReadContext is a context-aware reader for random numbers.
+func ReadContext(ctx context.Context, b []byte) (int, error) {
+	return Reader.ReadContext(ctx, b)
+}
+
+// ContextReader is a cancelable io.Reader.
+type ContextReader interface {
+	// Read behaves like a blocking io.Reader.Read.
+	//
+	// Read wraps ReadContext with a background context.
+	Read(b []byte) (n int, err error)
+
+	// ReadContext is an io.Reader that blocks until data is available or
+	// until ctx is done.
+	ReadContext(ctx context.Context, b []byte) (n int, err error)
+}
+
+// contextReader is a cancelable io.Reader.
+type contextReader interface {
+	ReadContext(context.Context, []byte) (int, error)
+}
+
+// ctxReader takes a contextReader and turns it into a ContextReader.
+type ctxReader struct {
+	contextReader
+	ctx context.Context //nolint:containedctx
+}
+
+func (cr ctxReader) Read(b []byte) (int, error) {
+	return cr.contextReader.ReadContext(cr.ctx, b)
+}
+
+// DefaultReaderWithContext returns a context-aware io.Reader.
+//
+// Because this stores the context, only use this in situations where an
+// io.Reader is unavoidable.
+func DefaultReaderWithContext(ctx context.Context) ContextReader {
+	return ctxReader{
+		ctx:           ctx,
+		contextReader: defaultContextReader,
+	}
+}