In Go, the function commonly used to handle errors by logging them and exiting the program is 'log.Fatal'. This function logs the error message and terminates the program.

In Go, if the type assertion fails, it will cause a panic. This means that if the type assertion does not hold true at runtime, the program will panic and may terminate abruptly. Therefore, it's essential to handle type assertion failures appropriately to avoid unexpected crashes in Go programs.

The "testing" package is commonly used for writing unit tests in Go. It provides various functions and utilities for creating and running tests, defining test cases, and asserting expected outcomes.

The '*' operator in Go is used for pointer dereferencing. It allows access to the value stored at the memory address pointed to by the pointer. For example, if 'ptr' is a pointer, '*ptr' accesses the value it points to.

Handling nil pointer dereference errors gracefully in Go requires explicit checking for nil pointers before attempting to dereference them. This helps avoid runtime panics. Implementing error logging and recovery mechanisms can also aid in gracefully handling such errors and preventing application crashes.

One of the key advantages of Gorilla Mux over the default HTTP router in Go is its flexibility. Gorilla Mux provides more advanced routing features, such as route patterns and constraints, which enhance flexibility.

Gorilla Mux can handle route parameters with different data types by using regular expressions in route patterns, allowing for more flexible and precise matching of URL patterns with specific data types.

Anonymous functions in Go are often referred to as unnamed functions because they lack a specific identifier or name. They can be defined inline without a name and are commonly used for tasks like defining callbacks or handling short-lived operations.

Gorm provides a feature called "raw SQL" which allows developers to execute SQL queries directly. This is useful for scenarios where Gorm's methods are insufficient to express the complexity of the query. Using raw SQL ensures compatibility with Gorm and leverages its connection management and mapping features.

The correct answer is net/http. This package in Go provides essential functionalities for working with HTTP servers and clients. It includes methods for creating HTTP servers, handling requests, and making HTTP requests to other servers. It is a fundamental package used in building web applications and services in Go. With the net/http package, you can easily create robust HTTP servers and clients with minimal effort, making it a core component of web development in Go.

While anonymous functions offer flexibility and convenience, they also come with some potential drawbacks. One such drawback is readability issues, as the code might become less clear when using complex anonymous functions. Additionally, debugging anonymous functions can be challenging, especially when they're deeply nested or capture a large amount of external state.

Isolation level defines the degree of isolation between concurrent transactions. It specifies how much one transaction should be isolated from the effects of other concurrent transactions. Higher isolation levels typically result in fewer concurrency effects but can also lead to more locking and resource contention.