Database/sql Packet Connection Pool interpretation

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Connection pooling is a concept that is often used for network applications, and can cache connections to reduce the loss of creating connections. So how to do a connection pool in Golang, here will be interpreted Database/sql package of connection pool implementation to give yourself some reference and inspiration.
First of all, you need to understand the basic principles of database/sql and how to use, please refer to the following links to read carefully: http://go-database-sql.org/overview.html