diff --git a/go.mod b/go.mod
index 96e8e9c..1357e37 100644
--- a/go.mod
+++ b/go.mod
@@ -4,3 +4,5 @@ require (
 	github.com/ipfs/go-block-format v0.0.2
 	github.com/ipfs/go-cid v0.0.3
 )
+
+go 1.13
diff --git a/interface.go b/interface.go
index c3032b2..e271793 100644
--- a/interface.go
+++ b/interface.go
@@ -31,7 +31,54 @@ type Fetcher interface {
 
 // SessionExchange is an exchange.Interface which supports
 // sessions.
+//
+// Deprecated: Use the free-function NewSession(ctx) to associate a session with
+// a context.
 type SessionExchange interface {
 	Interface
+
+	// Deprecated: Use the free-function NewSession(ctx) to associate a new session
+	// with a context and call functions on the normal exchange interface.
 	NewSession(context.Context) Fetcher
 }
+
+// SessionKey is an opaque type uniquely identifying a session. Each SessionKey
+// should be allocated with new(SessionKey).
+type SessionKey struct{}
+
+type sessionContextKey struct{}
+type sessionContextValue struct {
+	sesKey *SessionKey
+	sesCtx context.Context
+}
+
+// NewSession registers a new session with the context. The session will be
+// closed when the passed-in context is canceled.
+//
+// If there's already a session associated with the context, the existing
+// session will be used.
+//
+// This function does not initialize any state, it just creates a new
+// *SessionKey and associates it with the context.
+func NewSession(ctx context.Context) context.Context {
+	if _, ok := ctx.Value(sessionContextKey{}).(*sessionContextValue); ok {
+		// Leave the session alone.
+		return ctx
+	}
+	return context.WithValue(ctx, sessionContextKey{}, &sessionContextValue{
+		sesKey: new(SessionKey),
+		sesCtx: ctx, // save this so we can construct the session with the _session_ context.
+	})
+}
+
+// GetSession loads the fetcher from the context. The returned context is the
+// context associated with the session itself.
+//
+// If there is no session associated with this context, this function returns
+// a new session key and the passed-in context.
+func GetSession(ctx context.Context) (*SessionKey, context.Context) {
+	if s, ok := ctx.Value(sessionContextKey{}).(*sessionContextValue); ok {
+		return s.sesKey, s.sesCtx
+	}
+	return new(SessionKey), ctx
+}