Creating a custom error type can be beneficial when you want to reduce code duplication in error handling. For example, in a large codebase, you might encounter similar error-handling logic in multiple places. By creating a custom error type, you can encapsulate the common error handling code and reuse it throughout the application, which simplifies maintenance and ensures consistency in error handling. It also adheres to the DRY (Don't Repeat Yourself) principle, improving code quality.

The correct answer is encoding/json. In Go, the encoding/json package provides functionality to work with JSON data. This package allows you to encode Go values into JSON format and decode JSON data into Go values. It offers various functions and types for working with JSON, including Marshal and Unmarshal functions, which are commonly used for encoding and decoding JSON data.

A struct in Go is a collection of fields. Fields are variables that hold data within the struct. They define the structure or blueprint for the data that a struct can hold. While methods can be associated with structs, they are not part of the struct itself but can operate on the struct's fields. Interfaces define behavior, and constants are fixed values, neither of which is the primary content of a struct.

Data serialization and data deserialization are two complementary processes. Serialization is the process of converting structured data, such as objects or data structures, into a format that can be easily transmitted or stored, often in binary or text format. It prepares data for transportation or storage. On the other hand, deserialization is the process of taking serialized data and reconstructing it into its original structured form, effectively turning it back into usable data. In essence, serialization prepares data for export, while deserialization imports and makes it usable again within an application.

To ensure a map is safe to use concurrently from multiple goroutines in Go, you would typically use a mutex (mutual exclusion). A mutex helps synchronize access to the map, preventing data races and ensuring that only one goroutine can modify the map at a time. The correct option is (1) mutex.

Embedding structs within structs is beneficial in scenarios where there is a need for code reuse and maintaining a consistent data structure. In the e-commerce example, embedding a 'User' struct within 'Customer' and 'Admin' structs allows you to inherit common user attributes while adding role-specific fields, reducing redundancy and ensuring uniformity in user representation across the system. This approach simplifies user management.

When you attempt to access an element outside the bounds of an array or slice in Go, it results in a runtime panic. This can lead to a program crash if not handled properly. It's essential to check the bounds of your slices or arrays before accessing elements to avoid such panics and ensure the stability of your Go programs.

The go mod tidy command is used to tidy the go.mod file by removing any no longer needed dependencies. It analyzes the codebase to determine which dependencies are actually required by the project and removes any that are unused. This helps keep the go.mod file clean and prevents unnecessary dependencies from cluttering the project.

To debug a memory leak in a Go program, you should employ memory profiler tools such as 'pprof' and 'net/http/pprof.' These tools help you capture memory usage data during program execution. You can then analyze the data to identify memory allocation patterns, memory leaks, and memory-hungry parts of your code. By using these profiler tools, you can pinpoint the source of the memory leak and take corrective actions, such as freeing up unused memory or optimizing data structures. Disabling garbage collection is not a recommended approach, as it can lead to memory-related issues rather than solving them.

Sentinel errors are user-defined errors that are returned as specific values to indicate an error condition, while error types are user-defined error interfaces. Sentinel errors are often used for common, predefined errors, and error types allow for more detailed and structured error handling by creating custom error types that can carry additional context or information about the error.

Type assertions in Go are used to extract the underlying (concrete) value from an interface. When you have an interface value, you can use a type assertion to convert it back to its original type so that you can access its methods and properties. This is a common operation when working with interfaces, especially in cases where you need to work with specific methods or fields of the underlying type.

In a Go application for handling configurations, you can use a map to store and manage configuration settings by storing configuration keys as map keys and their corresponding values as map values. This allows you to quickly access configuration values using their associated keys. It's a flexible approach, as you can add, modify, or remove configuration settings dynamically by manipulating the map.