It is not friendly that the type of ExtraParams in struct Mapping is string in go-sdk

[ThreadDao]

Please state your issue using the following template and, most importantly, in English.

Describe the bug
It is not easy to unmarshal dimension from ExtraParams (string) when get_collection_info

// CollectionParam informations of a collection
type Mapping struct {
	// CollectionName collection name
	CollectionName string
	// Fields fields
	Fields []Field
	// ExtraParams extra params
	ExtraParams string
}

[{float 10 {} {"params":"null"}} {float_vector 101 {} {"params":"{\"dim\":128}"}}] {"params":"{\"auto_id\":false,\"segment_row_count\":5000,\"segment_row_limit\":524288}"}}

Steps/Code to reproduce behavior
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Expected behavior
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Method of installation

• Docker/cpu
• Docker/gpu
• Build from source

Environment details

• Hardware/Softwars conditions (OS, CPU, GPU, Memory)

• Milvus version (master or released version)
  -0.11.1

Configuration file
Settings you made in server_config.yaml or milvus.yaml

paste-file-content-here

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Additional context
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