In Go, a higher-order function is a function that can accept one or more functions as arguments or return a function. This capability allows for more flexible and modular code by enabling functions to be passed as parameters and returned as values.

Fields in a struct are accessed using dot notation in Go. This involves typing the name of the struct variable followed by a dot (.) and then the name of the field to access its value.

The correct option is Close. In Go's database/sql package, the Close method is used to close a database connection explicitly. It's essential to close connections properly to release resources and prevent leaks.

Version control systems like Git are commonly used to manage changes to database migration scripts, allowing for tracking, collaboration, and rollback.

Goroutine leaks can occur when a goroutine continues to run even after the surrounding function has returned. To prevent this, it's essential to ensure that all channels created within the goroutine are closed properly when they are no longer needed. This allows the garbage collector to reclaim the resources associated with the goroutine, preventing leaks and conserving memory.

In Go, the keyword func is used to define a method on a type. This allows functions to be associated with specific types, enabling a more object-oriented programming style in Go.

In Go, the function used to create a new slice by slicing an existing array or slice is the slice function. This function takes the original slice/array and specifies a range to create a new slice. make is used to create slices, maps, and channels with a specified length and capacity. append is used to add elements to a slice. copy is used to copy elements from one slice to another.

Optimizing configuration parameters can enhance the efficiency of database connection pooling. By fine-tuning parameters such as connection timeout, idle timeout, and maximum connections, the system can optimize resource usage and performance.

The correct answer is ListenAndServe. This method creates a new HTTP server and sets it to listen on the specified network address. It starts accepting incoming connections and serving HTTP requests. It takes in an address and a handler, allowing you to specify the network address to listen on and the handler to use to handle requests. This method is commonly used to start serving HTTP traffic in Go applications.

In Go, the '+' operator is used to concatenate strings. It concatenates two strings together to form a new string. The '&' operator is used for addressing, '*' for dereferencing, and '<<' for bit shifting.

In Go testing, 'Benchmark' functions are used specifically to measure the performance of code, typically by running it repeatedly. 'Example' functions, on the other hand, provide usage examples and are commonly utilized for generating documentation with the 'go doc' command. Finally, 'Test' functions are used for traditional unit testing, where various assertions are made to ensure the correctness of the code. Understanding the distinctions between these types of functions is crucial for effective testing in Go.

The correct option is "Query". The Query method is used to execute a SQL query that returns rows. It prepares the SQL statement and then executes it, returning a Rows result set for further processing.