Go SDK for EventMesh gRPC

[walleliu1016]

merge the golang sdk to master branch

#86 add golang sdk GRPC

• support webhook subscription and stream subscription
• support async and RR message
• only support eventmeshmessage now
• add multiple loadbalancer strategy, support multiple connection later
• add logger with zap.Logger
• support uuid and sonyflake to generate unique ID
• suport atomic.Seqence ID

TODO

• support cloudevent message
• support multiple eventmesh server connection

[qqeasonchen]

LGTM

[qqeasonchen]

@walleliu1016 please take a look about license check fail

[codecov]

Codecov Report

Merging #911 (bd77cc6) into master (755df48) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##             master    #911   +/-   ##
========================================
  Coverage      8.91%   8.91%           
  Complexity      529     529           
========================================
  Files           347     347           
  Lines         21773   21773           
  Branches       2426    2426           
========================================
  Hits           1941    1941           
  Misses        19682   19682           
  Partials        150     150           

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[qqeasonchen]

WARNING Failed to determine the comment style of file: eventmesh-sdk-go/go.sum
WARNING Failed to create review comment, fallback to a plain comment: POST https://api.github.com/repos/apache/incubator-eventmesh/pulls/911/reviews: 403 Resource not accessible by integration []
WARNING Failed to create review comments POST https://api.github.com/repos/apache/incubator-eventmesh/pulls/911/reviews: 403 Resource not accessible by integration []
ERROR the following files don't have a valid license header:
eventmesh-sdk-go/common/protocol/http/body/client/heartbeat_request_body.go
eventmesh-sdk-go/common/protocol/http/body/client/subscribe_request_body.go
eventmesh-sdk-go/common/seq/num.go
eventmesh-sdk-go/go.mod
eventmesh-sdk-go/go.sum
eventmesh-sdk-go/grpc/client_test.go
eventmesh-sdk-go/grpc/conf/config_test.go
eventmesh-sdk-go/grpc/heartbeat_test.go
eventmesh-sdk-go/grpc/loadbalancer/loadbalancer_test.go
eventmesh-sdk-go/grpc/loadbalancer/rule_iphash_test.go
eventmesh-sdk-go/grpc/loadbalancer/rule_random_test.go
eventmesh-sdk-go/grpc/loadbalancer/rule_roundrobin_test.go
eventmesh-sdk-go/grpc/loadbalancer/status_server_test.go
eventmesh-sdk-go/grpc/proto/eventmesh-client_grpc.pb.go

[qqeasonchen]

LGTM