About the Go language identifier

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　The go language has two conditions for references to identifiers in other packages; First, the package has been imported in advance, implemented through the Go Language import code, and the identifiers in the package must be exportable. And the identifier can be exported to meet the same two conditions; first uppercase, the go language is based on the case to determine access rights, the initial capitalization means that the access rights of the identifier is "public", lowercase indicates that access is "private", only the code in the same package can access; The identifier must be a variable or type name in the code package, or a field or method name in the struct.