In Go, the keyword 'var' is used to declare a variable. It's followed by the variable name and its type. For example, var age int declares a variable named 'age' of type 'int'. 'var' is a fundamental keyword in Go for variable declaration.

In Go, a closure is an anonymous function that captures and retains the surrounding state. This means it can access and manipulate variables defined outside of its body. Closures are commonly used in situations where you need to create functions with dynamic behavior that relies on external variables.

In Go, the convention for the receiver parameter in a method definition is to use a single letter that represents the type, often the first letter of the type's name. This parameter can be either a value or a pointer type, depending on whether the method needs to mutate the receiver.

Ginkgo is a popular testing framework in Go that enables developers to write behavior-driven tests using a natural language style. It provides clear and readable test cases, enhancing the readability of tests.

The correct option is registering a handler function for a specific route. http.HandleFunc is used to associate a handler function with a specific URL pattern. When a request matches the specified pattern, the associated handler function is called to handle the request.

Channels in Go can be synchronous or asynchronous and buffered or unbuffered. Synchronous channels block the sender until the receiver is ready, while asynchronous channels allow the sender to continue immediately. Buffered channels have a capacity, allowing multiple senders to store data without immediate consumption.

In Go, the 'errors.New()' function is used to create custom error messages. This function takes a string as input and returns a new error that implements the 'error' interface. It's commonly used when a specific error message needs to be returned from a function.

In Go, the defer keyword is used to defer the execution of a function until the surrounding function returns. It's commonly used to ensure cleanup actions are performed, such as closing files or unlocking mutexes.

In the database/sql package of Go, the interface used to represent a database row is Row. This interface provides methods to scan column values into Go variables. When executing a SQL query that returns rows, you typically use the QueryRow() method to fetch a single row and then scan its values using the Scan() method of the Row interface. The Row interface abstracts the notion of a database row, making it easy to work with individual rows of query results.

In Go, the keyword "func" is used to define a function. It precedes the function name and parameter list in a function declaration. For example, func functionName(parameters) returnType { ... }.