Why SOLID Doesn't Work in Golang
Too many engineers treat the SOLID principles as sacred. But Golang is not Java, not C#, and not a place for OOP dogma. Let's walk through each letter — and why blindly applying SOLID in Golang leads to bloated, fragile code.
S — Single Responsibility Principle
"A class should have only one reason to change."
Sounds clean — in a language with classes. But Golang has none. Just functions, structs, and packages.
Attempts to force SRP often result in fragmentation: FooService, FooServiceHelper, FooServiceAdapter, FooServiceImpl. It's not design — it's noise.
A better rule in Golang: If it fits in one file, is readable, and works — leave it alone. Avoid speculative separation. Solve actual problems.
O — Open/Closed Principle
"Open for extension, closed for modification."
In practice, this creates code that's too scared to change. Layers, wrappers, plugin architectures — all to avoid touching what could've just been fixed.
In Golang, one reads and edits real code. Modification is not a sin — it's part of maintenance.
If a change breaks everything downstream — the issue is coupling, not change. Good boundaries don't collapse when touched.
Protecting bad design with abstraction is not safety. It's fear.
L — Liskov Substitution Principle
"Subtypes must be substitutable for their base types."
Sounds fine — if your language has inheritance. Golang doesn't.
It has implicit interfaces, not base classes. One doesn't build hierarchies. One builds behavior.
Problems start when one creates giant interfaces and forces every type to fit. That's not substitution — that's coercion.
Golang promotes small, extracted interfaces based on usage. No need for rigid trees. No need for theoretical substitution.
LSP is fine — just not to be absolutized. Especially in Golang.
I — Interface Segregation Principle
"Clients should not depend on methods they don't use."
This isn't just a principle in Golang — it's idiomatic.
The standard library shows how it's done: io.Reader, io.Writer, io.Closer — small, focused, composable.
Trouble starts when one defines interfaces prematurely — for services, repositories, anything. One implementation. Dozens of mockable abstractions. No gain.
In Golang, good interfaces are minimal, practical, and driven by use. Not speculative. Not ceremonial.
ISP is practiced in Golang — not preached.
D — Dependency Inversion Principle
"High-level modules should depend on abstractions."
This often leads to forced indirection in Golang: interfaces with one implementation, constructors with 12 params, unreadable code.
But Golang doesn't need inversion frameworks. Dependencies are passed directly. Simple, clear, explicit.
Interfaces belong at the edges — for I/O, messaging, APIs. The core can stay concrete.
Abstraction is a tool. Not a default.
Final Thought
SOLID was designed for class-heavy, inheritance-based OOP. Golang chose another path: clarity over ceremony, composition over hierarchy, behavior over abstraction.
Following SOLID blindly in Golang creates complexity. Ignoring it — and writing code that's small, direct, and understandable — often results in something better:
Working software.