add the cache service (#112)

cache/proto/cache.proto

@@ -0,0 +1,89 @@
+syntax = "proto3";
+
+package cache;
+
+option go_package = "./proto;cache";
+
+service Cache {
+	rpc Get(GetRequest) returns (GetResponse) {}
+	rpc Set(SetRequest) returns (SetResponse) {}
+	rpc Delete(DeleteRequest) returns (DeleteResponse) {}
+	rpc Increment(IncrementRequest) returns (IncrementResponse) {}
+	rpc Decrement(DecrementRequest) returns (DecrementResponse) {}
+}
+
+message Item {
+	// The key
+	string key = 1;
+	// The value
+	string value = 2;
+	// Time to live in seconds
+	int64 ttl = 3;
+}
+
+// Get an item from the cache by key
+message GetRequest {
+	// The key to retrieve
+	string key = 1;
+}
+
+message GetResponse {
+	// The item in the cache
+	Item item = 1;
+}
+
+// Set an item in the cache
+message SetRequest {
+	// The key to update
+	string key = 1;
+	// The value to set
+	string value = 2;
+	// Time to live in seconds
+	int64 ttl = 3;
+}
+
+message SetResponse {
+	// Returns "ok" if successful
+	string status = 1;
+}
+
+// Delete a value from the cache
+message DeleteRequest {
+	// The key to delete
+	string key = 1;
+}
+
+message DeleteResponse {
+	// Returns "ok" if successful
+	string status = 1;
+}
+
+// Increment a value (if its a number)
+message IncrementRequest {
+	// The key to increment
+	string key = 1;
+	// The value to add
+	int64 value = 2;
+}
+
+message IncrementResponse {
+	// The key incremented
+	string key = 1;
+	// The result value
+	int64 value = 2;
+}
+
+// Decrement a value (if its a number)
+message DecrementRequest {
+	// The key to decrement
+	string key = 1;
+	// The delta value to decrement
+	int64 value = 2;
+}
+
+message DecrementResponse {
+	// The key of the item
+	string key = 1;
+	// The result value of the item
+	int64 value = 2;
+}