chore(perf): Optimize the Copy method of the Context struct (#3859)

* Optimize the Copy method of the Context struct: using 'make' to initialize the map('cp.Keys') with a length of 'c.Keys'; avoiding repeatedly assiging the 'params' to 'context'.

* Using temporary variables to save c.Keys and c.Params to prevent them from changing during the copying process.

---------

Co-authored-by: huangzw <[email protected]>

Author: 1911860538

context.go

@@ -113,20 +113,24 @@ func (c *Context) Copy() *Context {
 	cp := Context{
 		writermem: c.writermem,
 		Request:   c.Request,
-		Params:    c.Params,
 		engine:    c.engine,
 	}
+
 	cp.writermem.ResponseWriter = nil
 	cp.Writer = &cp.writermem
 	cp.index = abortIndex
 	cp.handlers = nil
-	cp.Keys = map[string]any{}
-	for k, v := range c.Keys {
+
+	cKeys := c.Keys
+	cp.Keys = make(map[string]any, len(cKeys))
+	for k, v := range cKeys {
 		cp.Keys[k] = v
 	}
-	paramCopy := make([]Param, len(cp.Params))
-	copy(paramCopy, cp.Params)
-	cp.Params = paramCopy
+
+	cParams := c.Params
+	cp.Params = make([]Param, len(cParams))
+	copy(cp.Params, cParams)
+
 	return &cp
 }