docs: update engine docs (#733)

Co-authored-by: kinggo <lilong.21@bytedance.com>
Co-authored-by: copy rogers <40619032+rogerogers@users.noreply.github.com>

content/en/docs/hertz/tutorials/basic-feature/context/request.md

@@ -906,7 +906,7 @@ h.POST("/user", func(c context.Context, ctx *app.RequestContext) {
 
 ### SetFormValueFunc
 
-Set the FormValue function.
+If the default method provided by the [FormValue](#formvalue) function to obtain the value of the key does not meet the requirements, users can use this function to customize the method of obtaining the value of the key.
 
 Function Signature:
 
@@ -1346,7 +1346,9 @@ h.Use(func(c context.Context, ctx *app.RequestContext) {
 
 ### SetClientIPFunc
 
-Set the address of the client IP.
+If the default method provided by the [ClientIP](#clientip) function does not meet the requirements, users can use this function to customize the way to obtain the client ip.
+
+This function can be used in scenarios where you want to obtain an ip from the `X-Forwarded-For` or `X-Real-IP` header even if a remote ip exists (multiple proxies, want to obtain the initial ip from the `X-Forwarded-For` or `X-Real-IP` header).
 
 Function Signature:
 

content/en/docs/hertz/tutorials/basic-feature/context/response.md

@@ -367,7 +367,7 @@ func (ctx *RequestContext) AbortWithStatusJSON(code int, jsonObj interface{})
 
 ### SetBodyStream
 
-Set Body Stream and optional Body Size.
+Set Body Stream and optional Body Size. This function is used for streaming processing on Hertz Server, as detailed in [Streaming](/docs/hertz/tutorials/basic-feature/engine/#streaming).
 
 > Note: When the bodySize is less than 0, all data is written. When it is greater than or equal to 0, data is written based on the set bodySize size.