SyncHttpClient constructor Null safety

1. Flutter
2. sync.http
3. SyncHttpClient
4. SyncHttpClient constructor

SyncHttpClient class

1. Constructors
2. SyncHttpClient
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Static methods
12. deleteUrl
13. getUrl
14. postUrl
15. putUrl