Caching policies added.

We used httpcache library to implement this. As it was not possible to support different policies, I mostly copied and modified it.

cache/memorycache/memorycache.go

@@ -0,0 +1,39 @@
+package memorycache
+
+import (
+	"sync"
+)
+
+// Cache is an implementation of Cache that stores responses in an in-memory map.
+type Cache struct {
+	mu    sync.RWMutex
+	items map[string][]byte
+}
+
+// Get returns the []byte representation of the response and true if present, false if not
+func (c *Cache) Get(key string) (resp []byte, ok bool) {
+	c.mu.RLock()
+	resp, ok = c.items[key]
+	c.mu.RUnlock()
+	return resp, ok
+}
+
+// Set saves response resp to the cache with key
+func (c *Cache) Set(key string, resp []byte) {
+	c.mu.Lock()
+	c.items[key] = resp
+	c.mu.Unlock()
+}
+
+// Delete removes key from the cache
+func (c *Cache) Delete(key string) {
+	c.mu.Lock()
+	delete(c.items, key)
+	c.mu.Unlock()
+}
+
+// New returns a new Cache that will store items in an in-memory map
+func New() *Cache {
+	c := &Cache{items: map[string][]byte{}}
+	return c
+}