An attempt at a concise explanation of Go’s reflect library.

The reflect package implements run-time reflection, allowing a program to check, amend and create arbitrary values of all kinds during implementation. Traditionally, Go is static, types are known and verified at compile time. The reflect package allows you to escape from this static world. It operates primarily on two concepts: reflect.Type, which represents the static properties of a type (like its name, methods, and struct fields), and reflect.Value, which holds the actual underlying data and allows for dynamic reading and writing.

You might want to use the reflect package if:

• You are writing code that must operate on types that are not known at compile time (e.g., a generic JSON marshaler, an object-relational mapper, or a dependency injection framework).
• You need to dynamically inspect the fields of a struct to implement generic validation logic.
• You are building powerful testing or mocking tools that need to instantiate or analyze arbitrary objects.

You might want to avoid or be very careful with the reflect package if:

• Performance is critical. Reflection-based operations are significantly slower than direct, statically-typed code.
• You value compile-time safety. Using reflect bypasses the static type checker; type errors will cause a run-time panic instead of a compile-time error.
• Code clarity is a priority. Code using reflection is often more complex and harder for other developers to understand and maintain.
• You believe you need it for a simple problem. There is often a simpler, type-safe solution using interfaces or code generation.