close method Null safety

1. Dart
2. dart:io
3. RawDatagramSocket
4. close abstract method

RawDatagramSocket class

1. Constructors
2. RawDatagramSocket
3. Properties
4. address
5. broadcastEnabled
6. first
7. hashCode
8. isBroadcast
9. isEmpty
10. last
11. length
12. multicastHops
13. multicastInterface
14. multicastLoopback
15. port
16. readEventsEnabled
17. runtimeType
18. single
19. writeEventsEnabled
20. Methods
21. any
22. asBroadcastStream
23. asyncExpand
24. asyncMap
25. cast
26. close
27. contains
28. distinct
29. drain
30. elementAt
31. every
32. expand
33. firstWhere
34. fold
35. forEach
36. getRawOption
37. handleError
38. join
39. joinMulticast
40. lastWhere
41. leaveMulticast
42. listen
43. map
44. noSuchMethod
45. pipe
46. receive
47. reduce
48. send
49. setRawOption
50. singleWhere
51. skip
52. skipWhile
53. take
54. takeWhile
55. timeout
56. toList
57. toSet
58. toString
59. transform
60. where
61. Operators
62. operator ==
63. Static methods
64. bind